Protein purification using displacement chromatography

ABSTRACT

Disclosed herein are compositions and methods for the isolation and purification of proteins from a sample. In particular, the present invention relates to compositions and methods for isolating and purifying proteins incorporating a displacement chromatographic step. The present invention is also directed toward pharmaceutical compositions comprising one or more antibodies purified by a method described herein.

1. BACKGROUND OF THE INVENTION

The large-scale, economic purification of proteins continues to present challenges for the biopharmaceutical industry. Therapeutic proteins are typically produced using engineered prokaryotic or eukaryotic cell lines to express proteins of interest from a recombinant plasmid containing the gene encoding the protein. The cell culture processes used for producing those therapeutic proteins are known to produce proteins with varying degree of heterogeneity with respect to process-related impurities and product-related substances. Product-related substances typically include charge variants, aggregates, fragments, or other protein product species derived from alternative post-translational modifications. Process-related impurities include, for example, host cell proteins (HCPs), DNA, endotoxin, virus and cell culture media components. Control over such process-related impurities and product-related substances can impact numerous product characteristics, including, but not limited to, product stability, product safety and product efficacy.

Although various techniques are available for large-scale protein purification, the separation of product-related substances, including charge variant species, remains challenging. For example, the charge variants in monoclonal antibody preparations typically include acidic, main and basic species, which can be detected by WCX-10 HPLC (a weak cation exchange chromatography) or IEF (isoelectric focusing). The very similar physio-chemical characteristics between the main protein species and the acidic and basic variant species require the use of highly selective separation systems and methods in order to achieve efficient separation.

Displacement chromatography is a chromatographic separation technology that involves the use of a displacer molecule to aid in the separation of a mixture, e.g., an antibody-containing solution derived from cell culture harvest. The displacer molecule is conventionally selected to have a higher affinity for the stationary phase (i.e., the chromatographic support) as compared to the components present in the material to be separated. Due to its higher affinity, the displacer molecule competes with protein mixture components for the binding sites on the stationary phase. Under appropriate conditions, the displacer induces the components of the mixture to develop into consecutive zones of concentrated and purified species in the order of decreasing binding affinity ahead of the displacer front. This ordered displacement of the components of the mixture results in the formation of a so-called “displacement train.” In contrast to traditional elution mode chromatography, the displacement process takes advantage of the nonlinearity of the adsorption isotherm, allowing for higher column loading levels without compromising the purity and recovery of the component of interest. Finally, washing of the displacement train with the displacing buffer from the column allows for the component of interest to be isolated by collecting (and pooling if necessary) the proper fraction(s) of the displaced eluate. Displacement chromatography in described, in general, in Brgles et al., Journal of Chromatography A, 1218 (2011) 2389-2395; Gajdosik et al., Journal of Chromatography A, 1239 (2012) 1-9; Gerstner et al., Biotechnol. Prog., (1992), 8, 540-545; Kundu et al., Analytical Biochemistry, 248, 111-116, (1997); and Vogt et al., Journal of Chromatography A, 760 (1997) 125-137.

2. SUMMARY OF THE INVENTION

The present invention is directed to compositions and methods that control (modulate or reduce) process-related impurity and product-related substance heterogeneity in a population of proteins.

In certain embodiments, the instant invention is directed to methods and compositions for producing a sample comprising a protein of interest wherein the process-related impurity and product-related substance heterogeneity is modulated or reduced. In certain embodiments the product-related substances include, but are not limited to charge variants. Such charge variants can be acidic species (also referred to herein as “acidic regions” and “AR”) or basic species. In certain embodiments, the basic species are antibody species having C-terminal Lysines on both heavy chain sequences (“Lys 2”) or antibody species having a C-terminal Lysine on one heavy chain sequence (“Lys 1”), and such basic species can be contrasted with antibody species having no C-terminal Lysines (“Lys 0”). In certain embodiments, such methods comprise: (a) contacting a sample comprising the protein of interest and at least one process-related impurity and/or product-related substance to a chromatography media under conditions wherein the protein of interest binds to the chromatography media; (b) displacing the protein of interest bound to the chromatography media with at least one displacer molecule; and (c) collecting a chromatography sample, wherein the chromatography sample comprises a reduced heterogeneity of the distribution of process-related impurities and product-related substances. In certain embodiments, the chromatography media is selected from the group consisting of an ion exchange adsorbent material, e.g., a cation exchange (CEX) adsorbent material or an anion exchange (AEX) adsorbent material, and a multimodal adsorbent material, or a combination thereof. In certain embodiments of the present invention, the CEX resin is the Poros XS resin. In certain embodiments of the present invention, the mixed mode resin is the Capto MMC resin.

In certain embodiments of the present invention, the pH of the displacing wash buffer is lower than the isoelectric point of the protein of interest. In certain embodiments of the present invention, the pH of the displacing wash buffer is in the range of about 5.0 to about 9.0 or about 6.0 to about 8.0. In certain embodiments of the present invention, the conductivity of the wash buffer is between about 1 to about 86 mS/cm. In certain embodiments of the present invention, the conductivity of the wash buffer is in the range of about 2 to about 20 mS/cm. In certain embodiments of the present invention, the column length is in the range of about 10 to about 30 cm. In certain embodiments of the present invention, the flow residence time is in the range of about 5 minutes to about 20 minutes.

In certain embodiments of the present invention, the displacer in the wash buffer carries positive charge. In certain embodiments of the present invention, the cationic displacer in the wash buffer is a quaternary ammonium salt. In certain embodiments of the present invention, the quaternary ammonium salt is Expell SP1™. In certain embodiments of the present invention, the cationic displacer in the wash buffer is protamine sulfate. In certain embodiments of the present invention, the concentration of the displacer in the wash buffer is greater than about 0.1 mM. In certain embodiments of the present invention, the concentration of the Expell SP1™ in the wash buffer is in the range of about 0.1 to about 10 mM. In certain embodiments of the present invention, the concentration of the protamine sulfate in the wash buffer is in the range of about 0.1 to about 5 mM.

In certain embodiments of the present invention, one displacer buffer is used. In certain embodiments of the present invention, two or more displacing buffers consisting of different displacer concentrations are used. In certain embodiments of the present invention, the first displacing buffer containing about 0.5 mM Expell SP1™. In certain embodiments of the present invention, the first displacing buffer containing about 0.25 mM protamine sulfate. In certain embodiments of the present invention, two or more displacing buffers consisting of different displacer concentrations are used and the first displacing buffer contains lower displacer concentration than the second or subsequent displacing buffer. In certain embodiments of the present invention, mixtures of two or more displacers are used. In certain embodiments the displacers can be at the same or different concentrations. In certain embodiments of the present invention, different displacers are used in each of the multi-step displacing buffer for separation.

In certain embodiments of the present invention, the displacement operation is run in one-step displacement chromatography mode. In certain embodiments of the present invention, the displacement operation is run in two-step displacement chromatography mode. In certain embodiments of the present invention, the displacement operation is run in multiple-step displacement chromatography mode. In certain embodiments of the present invention, the displacement operation is run in linear gradient displacement chromatography mode.

In certain embodiments, displacement chromatography is used as the sole method of purification of the protein of interest. In certain embodiments, displacement chromatography is used in combination with other purification strategies, such as, but not limited to, the alternative techniques described herein, to reduce process-related impurities and/or other product-related substances.

In certain embodiments, fractions are collected during the displacement step and are combined (pooled) after appropriate analysis to provide a protein preparation that contains a desired level of the protein of interest and which can include one or more process-related impurities and/or other product-related substances. In certain embodiments, one or more process monitoring tools can be used in connection with the techniques described herein to facilitate the identification of an effective product pooling strategy. In certain embodiments, such monitoring can include on-line or in-line process monitoring. For example, but not by way of limitation, spectroscopy methods such as UV, NIR, FTIR, Fluorescence, and Raman may be used to monitor levels of product-related species, e.g., acidic species and lysine variants, in an on-line, at line or in-line mode. In certain embodiments, specific signals arising from the chemical modification of the proteins such as glycation, MGO modification, deamidation, glycosylation may be specifically measurable by spectroscopic methods through such in-line, on-line or at-line methods, enabling real time or near-real time control of product quality of the resulting product.

In certain embodiments, purification and/or pooling allows for the reduction of process-related impurities and/or other product-related substances. In certain embodiments, the purification and/or pooling techniques described herein allow for reduction of process-related impurities and the selective inclusion of particular product-related substances. For example, but not by way of limitation, the purification and/or pooling techniques allow for modulation of the concentration of product-related substances in the purified sample, e.g., increasing or decreasing the amount of acidic and/or basic species. In certain embodiments, the concentration of particular acidic and/or basic species, e.g., Lys0, Lys1, and/or Lys2, are modulated (increased or decreased) in the purified sample. In certain embodiments, such techniques can be used to ensure product uniformity over the course of multiple production runs.

In certain embodiments of the present invention, the chromatography separation produces samples containing reduced level of acidic species as compared to the starting load material. In certain embodiments of the present invention, the chromatography separation produces samples containing reduced level of protein aggregates as compared to the starting load material. In certain embodiments of the present invention, the chromatography separation produces samples containing reduced level of protein fragments as compared to the starting load material. In certain embodiments of the present invention, the chromatography separation produces samples containing reduced level of host cell proteins as compared to the starting load material. In certain embodiments of the present invention, the chromatography separation produces samples containing different levels of basic variants from the starting load material. In certain embodiments of the present invention, the chromatography separation produces samples containing reduced levels of acidic variants, aggregates, fragments and HCPs from the starting load material.

In certain embodiments of the present invention, the protein of interest is an anti-TNFα antibody, such as Adalimumab.

3. BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 depicts (a) comparison of a desired and an undesired displacement chromatogram for Adalimumab on Poros XS resin using Expell SP1™; (b) charge variants distribution in eluate fractions derived from the undesired displacement chromatography process for Adalimumab (Poros XS resin & Expell SP1™)

FIG. 2 depicts CEX-HPLC chromatograms of Expell SP1™-displaced Adalimumab sample fractions.

FIG. 3 depicts the separation of Adalimumab charge variants by Poros XS displacement chromatography using Expell SP1™.

FIG. 4 depicts the reduction of acidic species level in Adalimumab by Poros XS displacement chromatography using Expell SP1™.

FIG. 5 depicts the effect of Expell SP1™ concentration on acidic species reduction in Adalimumab by Poros XS displacement chromatography.

FIG. 6 depicts the effect of pH on acidic species reduction in Adalimumab by Poros XS displacement chromatography using Expell SP1™.

FIG. 7 depicts the reduction of acidic species level in Adalimumab by Poros XS two-step displacement chromatography using Expell SP1™.

FIG. 8 depicts the separation of Adalimumab size variants by Poros XS displacement chromatography using Expell SP1™.

FIG. 9 depicts the separation of HCP in Adalimumab by Poros XS displacement chromatography using Expell SP1™.

FIG. 10 depicts the separation of Adalimumab charge variants by Poros XS displacement chromatography using protamine sulfate.

FIG. 11 depicts the reduction of acidic species in Adalimumab by Poros XS displacement chromatography using protamine sulfate.

FIG. 12 depicts the effect of protamine sulfate concentration on acidic species reduction in Adalimumab by Poros XS displacement chromatography.

FIG. 13 depicts the effect of pH on acidic species reduction in Adalimumab by Poros XS displacement chromatography using protamine sulfate.

FIG. 14 depicts the reduction of acidic species in Adalimumab by Poros XS two-step displacement chromatography using protamine sulfate.

FIG. 15 depicts the reduction of acidic species in Adalimumab on Poros XS using protamine sulfate linear gradient displacement chromatography.

FIG. 16 depicts the separation of Adalimumab size variants by Poros XS displacement chromatography using protamine sulfate.

FIG. 17 depicts the separation of mAb X charge variants by Poros XS displacement chromatography using Expell SP1™.

FIG. 18 depicts the reduction of acidic species in mAb X by Poros XS displacement chromatography using Expell SP1™.

FIG. 19 depicts the effect of Expell SP1™ concentration on acidic species reduction in mAb X by Poros XS displacement chromatography.

FIG. 20 depicts the reduction of acidic species in mAb X by Poros XS two-step displacement chromatography using Expell SP1™.

FIG. 21 depicts the separation of mAb X charge variants by Poros XS displacement chromatography using protamine sulfate.

FIG. 22 depicts the reduction of acidic species in mAb X by Poros XS displacement chromatography using protamine sulfate.

FIG. 23 depicts the effect of protamine sulfate concentration on acidic species reduction in mAb X by Poros XS displacement chromatography.

FIG. 24 depicts the reduction of acidic species in mAb X by Poros XS two-step displacement chromatography using protamine sulfate.

FIG. 25 depicts the separation of mAb X size variants by Poros XS displacement chromatography using protamine sulfate.

FIG. 26 depicts the separation of mAb Y charge variants by Poros XS displacement chromatography using Expell SP1™.

FIG. 27 depicts the reduction of acidic species in mAb Y by Poros XS displacement chromatography using Expell SP1™.

FIG. 28 depicts the separation of Adalimumab charge variants by Capto MMC displacement chromatography using protamine sulfate.

FIG. 29 depicts the reduction of acidic species in Adalimumab by Capto MMC displacement chromatography using protamine sulfate.

FIG. 30 depicts the separation of mAb X charge variants by Capto MMC displacement chromatography using protamine sulfate.

FIG. 31 depicts the reduction of acidic species in mAb X by Capto MMC displacement chromatography using protamine sulfate.

FIG. 32 depicts the effect of pH on acidic species reduction in mAb X by Capto MMC displacement chromatography.

FIG. 33 depicts the AR Growth at 25° C. of low and high AR containing samples.

4. DETAILED DESCRIPTION OF THE INVENTION

An objective of the present invention is to provide a method for isolating and purifying proteins from various process-related impurities and product-related substances including, but not limited to, undesired charge variants, size variants (aggregates and fragments) and HCPs at preparative scale using ion exchange displacement chromatography. A further objective of the present invention is to improve the applicability the displacement chromatography technology to large-scale protein purification by reducing required buffer volume for a given separation thereby improving the process efficiency. Another objective of the present invention is to demonstrate the use of mixed mode resin for displacement separation of proteins from various impurities.

In certain embodiments, the present invention is directed to methods and compositions for the purification of proteins, for example, but not limited to, antibodies (e.g., Adalimumab), from process-related impurities and product-related substances. In certain embodiments, the invention is directed to processes where a process stream, e.g., a partially purified antibody composition derived from cell culture harvest solution, is applied to a preparative scale ion exchange adsorbent, e.g., a cation exchange adsorbant (“CEX”), an anion exchange (“AEX”) adsorbent, or multimodal (“MM”) adsorbent under appropriate conditions. For example, but not by way of limitation, such conditions can include where the pH of the loading and equilibration/wash buffer is below the pI of the target protein to permit the target protein and impurities to bind to the adsorbent, e.g., a CEX adsorbent or a multimodal adsorbent. In certain embodiments, such conditions can also include where a displacing buffer is employed at a pH that is also below the pI of the target protein. In certain embodiments, such conditions can also include where the length of the column employed for the displacement separation is within the practical range of column bed height for large scale processing (i.e. ≦about 30 cm). In certain embodiments, such conditions can also include where the flow residence time employed for the displacement separation is less than about 25 minutes. In certain embodiments, such conditions can also include where a displacer concentration of an appropriately selected displacer is employed to induce the enrichment and separation of the target protein and impurities. In certain embodiments, such conditions can include collecting the displaced sample eluate after at least 10% of the total loaded protein mass has been displaced off the column. In certain embodiments, such conditions can also include the use of a multi-step displacer concentration during displacement in order to render manufacturability by reducing the required buffer volume and process time to a more practical range while achieving desired impurity clearance. In certain embodiments, such conditions can also include the use of a linear gradient displacer concentration to achieve the desired impurities clearance.

For clarity and not by way of limitation, this detailed description is divided into the following sub-portions:

-   -   4.1. Definitions;     -   4.2. Antibody Generation;     -   4.3. Antibody Production;     -   4.4. Antibody Purification;     -   4.5. Methods of Assaying Sample Purity;     -   4.6. Further Modifications; and     -   4.7. Pharmaceutical Compositions

4.1. Definitions

In order that the present invention may be more readily understood, certain terms are first defined.

The term “product”, as used herein refers to a protein of interest, which may be present in the context of a sample comprising one or more process-related impurities and/or product-related substances. In certain embodiments, the product, i.e., the protein of interest, is an antibody or antigen binding fragment thereof.

The term “antibody” includes an immunoglobulin molecule comprised of four polypeptide chains, two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds. Each heavy chain is comprised of a heavy chain variable region (abbreviated herein as HCVR or VH) and a heavy chain constant region (CH). The heavy chain constant region is comprised of three domains, CH1, CH2 and CH3. Each light chain is comprised of a light chain variable region (abbreviated herein as LCVR or VL) and a light chain constant region. The light chain constant region is comprised of one domain, CL. The VH and VL regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDRs), interspersed with regions that are more conserved, termed framework regions (FR). Each VH and VL is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The term “antibody”, as used herein, also includes alternative antibody and antibody-like structures, such as, but not limited to, dual variable domain antibodies (DVD-Ig).

The term “antigen-binding portion” of an antibody (or “antibody portion”) includes fragments of an antibody that retain the ability to specifically bind to an antigen (e.g., hIL-12, hTNFα, or hIL-18). It has been shown that the antigen-binding function of an antibody can be performed by fragments of a full-length antibody. Examples of binding fragments encompassed within the term “antigen-binding portion” of an antibody include (i) a Fab fragment, a monovalent fragment comprising the VL, VH, CL and CH1 domains; (ii) a F(ab′)2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment comprising the VH and CH1 domains; (iv) a Fv fragment comprising the VL and VH domains of a single arm of an antibody, (v) a dAb fragment (Ward et al., (1989) Nature 341:544-546, the entire teaching of which is incorporated herein by reference), which comprises a VH domain; and (vi) an isolated complementarity determining region (CDR). Furthermore, although the two domains of the Fv fragment, VL and VH, are coded for by separate genes, they can be joined, using recombinant methods, by a synthetic linker that enables them to be made as a single protein chain in which the VL and VH regions pair to form monovalent molecules (known as single chain Fv (scFv); see, e.g., Bird et al. (1988) Science 242:423-426; and Huston et al. (1988) Proc. Natl. Acad. Sci. USA 85:5879-5883, the entire teachings of which are incorporated herein by reference). Such single chain antibodies are also intended to be encompassed within the term “antigen-binding portion” of an antibody. Other forms of single chain antibodies, such as diabodies are also encompassed. Diabodies are bivalent, bispecific antibodies in which VH and VL domains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen binding sites (see, e.g., Holliger, P., et al. (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448; Poljak, R. J., et al. (1994) Structure 2:1121-1123, the entire teachings of which are incorporated herein by reference). Still further, an antibody may be part of a larger immunoadhesion molecule, formed by covalent or non-covalent association of the antibody with one or more other proteins or peptides. Examples of such immunoadhesion molecules include use of the streptavidin core region to make a tetrameric scFv molecule (Kipriyanov, S. M., et al. (1995) Human Antibodies and Hybridomas 6:93-101, the entire teaching of which is incorporated herein by reference) and use of a cysteine residue, a marker peptide and a C-terminal polyhistidine tag to make bivalent and biotinylated scFv molecules (Kipriyanov, S. M., et al. (1994) Mol. Immunol. 31:1047-1058, the entire teaching of which is incorporated herein by reference). Antibody portions, such as Fab and F(ab′)2 fragments, can be prepared from whole antibodies using conventional techniques, such as papain or pepsin digestion, respectively, of whole antibodies. Moreover, antibodies, antibody portions and immunoadhesion molecules can be obtained using standard recombinant DNA techniques, as described herein. In one aspect, the antigen binding portions are complete domains or pairs of complete domains.

The terms “Kabat numbering” “Kabat definitions” and “Kabat labeling” are used interchangeably herein. These terms, which are recognized in the art, refer to a system of numbering amino acid residues which are more variable (i.e., hypervariable) than other amino acid residues in the heavy and light chain variable regions of an antibody, or an antigen binding portion thereof (Kabat et al. (1971) Ann. NY Acad, Sci. 190:382-391 and, Kabat, E. A., et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242, the entire teachings of which are incorporated herein by reference). For the heavy chain variable region, the hypervariable region ranges from amino acid positions 31 to 35 for CDR1, amino acid positions 50 to 65 for CDR2, and amino acid positions 95 to 102 for CDR3. For the light chain variable region, the hypervariable region ranges from amino acid positions 24 to 34 for CDR1, amino acid positions 50 to 56 for CDR2, and amino acid positions 89 to 97 for CDR3.

The term “human antibody” includes antibodies having variable and constant regions corresponding to human germline immunoglobulin sequences as described by Kabat et al. (See Kabat, et al. (1991) Sequences of proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242). The human antibodies of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), e.g., in the CDRs and in particular CDR3. The mutations can be introduced using the “selective mutagenesis approach.” The human antibody can have at least one position replaced with an amino acid residue, e.g., an activity enhancing amino acid residue which is not encoded by the human germline immunoglobulin sequence. The human antibody can have up to twenty positions replaced with amino acid residues which are not part of the human germline immunoglobulin sequence. In other embodiments, up to ten, up to five, up to three or up to two positions are replaced. In one embodiment, these replacements are within the CDR regions. However, the term “human antibody”, as used herein, is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, have been grafted onto human framework sequences.

The phrase “recombinant human antibody” includes human antibodies that are prepared, expressed, created or isolated by recombinant means, such as antibodies expressed using a recombinant expression vector transfected into a host cell, antibodies isolated from a recombinant, combinatorial human antibody library, antibodies isolated from an animal (e.g., a mouse) that is transgenic for human immunoglobulin genes (see, e.g., Taylor, L. D., et al. (1992) Nucl. Acids Res. 20:6287-6295, the entire teaching of which is incorporated herein by reference) or antibodies prepared, expressed, created or isolated by any other means that involves splicing of human immunoglobulin gene sequences to other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences (see, Kabat, E. A., et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242). In certain embodiments, however, such recombinant human antibodies are subjected to in vitro mutagenesis (or, when an animal transgenic for human Ig sequences is used, in vivo somatic mutagenesis) and thus the amino acid sequences of the VH and VL regions of the recombinant antibodies are sequences that, while derived from and related to human germline VH and VL sequences, may not naturally exist within the human antibody germline repertoire in vivo. In certain embodiments, however, such recombinant antibodies are the result of selective mutagenesis approach or back-mutation or both.

An “isolated antibody” includes an antibody that is substantially free of other antibodies having different antigenic specificities. Moreover, an isolated antibody may be substantially free of other cellular material and/or chemicals.

The term “Koff”, as used herein, is intended to refer to the off rate constant for dissociation of an antibody from the antibody/antigen complex.

The term “Kd”, as used herein, is intended to refer to the dissociation constant of a particular antibody-antigen interaction.

The phrase “nucleic acid molecule” includes DNA molecules and RNA molecules. A nucleic acid molecule may be single-stranded or double-stranded, but in one aspect is double-stranded DNA.

The phrase “isolated nucleic acid molecule,” as used herein in reference to nucleic acids encoding antibodies or antibody portions (e.g., VH, VL, CDR3). The phrase “isolated nucleic acid molecule” is also intended to include sequences encoding bivalent, bispecific antibodies, such as diabodies in which VH and VL regions contain no other sequences other than the sequences of the diabody.

The phrase “recombinant host cell” (or simply “host cell”) includes a cell into which a recombinant expression vector has been introduced. It should be understood that such terms are intended to refer not only to the particular subject cell but to the progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term “host cell” as used herein.

The term “host cell proteins” (HCPs), as used herein, is intended to refer to non-target protein-related, proteinaceous impurities derived from host cells.

The term “modifying”, as used herein, is intended to refer to changing one or more amino acids in the antibodies or antigen-binding portions thereof. The change can be produced by adding, substituting or deleting an amino acid at one or more positions. The change can be produced using known techniques, such as PCR mutagenesis.

The term “about”, as used herein, is intended to refer to ranges of approximately 10-20% greater than or less than the referenced value. In certain circumstances, one of skill in the art will recognize that, due to the nature of the referenced value, the term “about” can mean more or less than a 10-20% deviation from that value.

The term “preparative scale”, as used herein, refers to a scale of purification operation that can be readily scaled-up and implemented at large scale manufacturing while still providing desired separation. For instance, one skilled in the field may develop a process using, e.g., a 0.5 cm (i.d.)×20 cm (L) column in the lab, and transfer it to large scale production using, e.g., a 30 cm (i.d.)×20 cm (L) column packed with the same resin and operated with the same set of buffers, same linear flow rates (or residence times) and buffer volumes. In preparative scale separation, column bed height is typically ≦about 30 cm and column pressure drop ≦about 5 bar.

The phrase “displacer molecule”, as used herein, refers to a molecule employed to displace from the chromatographic support components of the mixture to be separated. Selection of a particular displacer molecule will therefore be dependent on the chromatographic support employed as well as the protein system. Regardless of which chromatographic support is employed, displacer molecules will generally be selected such that they have a high affinity for the support. However, in certain embodiments, a displacer molecule may be selected that has a reduced affinity for the support, so long as it retains the ability to induce a displacement train that includes the protein of interest. In certain non-limiting embodiments, the displacer molecule will be employed in the context of protein separations in ion exchange chromatography and can be selected from, but are not limited to, the group consisting of: polyelectrolytes; polysaccharides; low-molecular-mass dendrimers; amino acids; peptide; antibiotics; and aminoglycosidepolyamines. In certain embodiments the displacer is selected from, but are not limited to, the group consisting of: Expell SP1™ (for CEX and for mixed mode); Expell Q3 (for anion-exchange chromatography (AEX) and for mixed mode); Propel Q2 (for AEX and for mixed mode); and protamine sulfate (for CEX and for mixed mode). Exemplary displacer molecules are described in U.S. Pat. No. 7,632,409, WO 99/47574, WO 03074148, WO 2007/055896, WO 2007/064809; and U.S. Pat. No. 6,881,540.

The tern “aggregates” used herein means agglomeration or oligomerization of two or more individual molecules, including but not limiting to, protein dimers, trimers, tetramers, oligomers and other high molecular weight species. Protein aggregates can be soluble or insoluble.

The term “fragments” used herein refers to any truncated protein species from the target molecule due to dissociation of peptide chain, enzymatic and/or chemical modifications. For instance, antibody fragments include, but not limited to, Fab, F(ab′)₂, Fv, scFv, Fd, dAb, or other compositions that contain a portion of the antibody molecule.

The term “charge variants”, as used herein, refers to the full complement of product variants including, but not limited to acidic species, and basic species (e.g., Lys variants). In certain embodiments, such variants can include product aggregates and/or product fragments, to the extent that such aggregation and/or fragmentation results in a product charge variation.

As used herein, the term “lysine variant heterogeneity” refers to a characteristic of a population of proteins wherein the population consists of proteins of substantially identical amino acid sequence, but where the population exhibits variation in the presence or absence of C-terminal lysine residues.

In certain embodiments, the protein is an antibody, and the distribution of lysine variant heterogeneity comprises a distribution of the lysine variants Lys 0, Lys 1 and Lys 2, wherein the Lys 0 lysine variant comprises an antibody with heavy chains that do not comprise a C-terminal lysine, wherein the Lys 1 lysine variant comprises an antibody with one heavy chain that comprises a C-terminal lysine, and wherein the Lys 2 lysine variant comprises an antibody wherein both heavy chains comprise a C-terminal lysine.

In certain embodiments, C-terminal lysine variants are associated with charge heterogeneities present in protein preparations, for example, monoclonal antibody (mAb) preparations, produced through a cell culture process. These heterogeneities can be detected by various methods, such as, for example, WCX-10 HPLC (a weak cation exchange chromatography), or IEF (isoelectric focusing).

In certain embodiments, the heterogeneity arises from subspecies of protein differing by the presence or absence of C-terminal lysines. For example, the population of proteins may comprise more than one subspecies of lysine variant. In one non-limiting example, the lysine variants may comprise at least two of Lys 0, Lys 1 and Lys 2 lysine variants which can be detected by weak cation exchange chromatography of the expression product of a host cell expressing Adalimumab.

In certain embodiments, the heterogeneity arises from the size of subpopulations having different C-terminal lysine profiles. For example, the population of proteins may comprise more than one subspecies of C-terminal lysine variant, and each of the variants may be present in different amounts. In one non-limiting example, the C-terminal lysine variants may be at least two of the Lys 0, Lys 1 and Lys 2 lysine variants detected by weak cation exchange chromatography of the expression product of a host cell expressing Adalimumab. In certain embodiments, Lys 0, Lys 1 or Lys 2 subspecies are present in different amounts.

In certain embodiments, the heterogeneity arises from both a difference in the amount of lysine variants in the population of proteins and the type of lysine variants present in the population of proteins.

As used herein, the terms “acidic species”, “acidic region” and “acidic species heterogeneity” refer to a characteristic of a population of proteins wherein the population includes a distribution of product-related substances identifiable by the presence of charge heterogeneities. For example, in monoclonal antibody (mAb) preparations, such acidic species heterogeneities can be detected by various methods, such as, for example, WCX-10 HPLC (a weak cation exchange chromatography), or IEF (isoelectric focusing). In certain embodiments, the acidic species identified using such techniques comprise a mixture of product-related impurities containing antibody product fragments (e.g., Fc and Fab fragments), aggregates, and/or post-translation modifications of the antibody product, such as, deamidated and/or glyco slyated antibodies.

In certain embodiments, the acidic species heterogeneity comprises a difference in the type of acidic species present in the population of proteins. For example, the population of proteins may comprise more than one acidic species variant.

In certain embodiments, the heterogeneity of the distribution of acidic species comprises a difference in the amount of acidic species in the population of proteins. For example, the population of proteins may comprise more than one acidic species variant, and each of the variants may be present in different amounts.

4.2. Antibody Generation

The term “antibody” as used in this section refers to an intact antibody or an antigen binding fragment thereof.

The antibodies of the present disclosure can be generated by a variety of techniques, including immunization of an animal with the antigen of interest followed by conventional monoclonal antibody methodologies e.g., the standard somatic cell hybridization technique of Kohler and Milstein (1975) Nature 256: 495. Although somatic cell hybridization procedures are preferred, in principle, other techniques for producing monoclonal antibody can be employed e.g., viral or oncogenic transformation of B lymphocytes.

One animal system for preparing hybridomas is the murine system. Hybridoma production is a very well-established procedure. Immunization protocols and techniques for isolation of immunized splenocytes for fusion are known in the art. Fusion partners (e.g., murine myeloma cells) and fusion procedures are also known.

An antibody can be a human, a chimeric, or a humanized antibody. Humanized antibodies of the present disclosure can be prepared based on the sequence of a non-human monoclonal antibody prepared as described above. DNA encoding the heavy and light chain immunoglobulins can be obtained from the non-human hybridoma of interest and engineered to contain non-murine (e.g., human) immunoglobulin sequences using standard molecular biology techniques. For example, to create a chimeric antibody, murine variable regions can be linked to human constant regions using methods known in the art (see e.g., U.S. Pat. No. 4,816,567 to Cabilly et al.). To create a humanized antibody, murine CDR regions can be inserted into a human framework using methods known in the art (see e.g., U.S. Pat. No. 5,225,539 to Winter, and U.S. Pat. Nos. 5,530,101; 5,585,089; 5,693,762 and 6,180,370 to Queen et al.).

Human monoclonal antibodies can be generated using transgenic or transchromosomic mice carrying parts of the human immune system rather than the mouse system. These transgenic and transchromosomic mice include mice referred to herein as the HuMAb Mouse® (Medarex, Inc.), KM Mouse® (Medarex, Inc.), and XenoMouse® (Amgen).

Moreover, alternative transchromosomic animal systems expressing human immunoglobulin genes are available in the art and can be used to raise antibodies of the disclosure. For example, mice carrying both a human heavy chain transchromosome and a human light chain tranchromosome, referred to as “TC mice” can be used; such mice are described in Tomizuka et al. (2000) Proc. Natl. Acad. Sci. USA 97:722-727. Furthermore, cows carrying human heavy and light chain transchromosomes have been described in the art (e.g., Kuroiwa et al. (2002) Nature Biotechnology 20:889-894 and PCT application No. WO 2002/092812) and can be used to raise the antibodies of this disclosure.

In one embodiment, the antibodies of this disclosure are recombinant human antibodies, which can be isolated by screening of a recombinant combinatorial antibody library, e.g., a scFv phage display library, prepared using human VL and VH cDNAs prepared from mRNA derived from human lymphocytes. Methodologies for preparing and screening such libraries are known in the art. In addition to commercially available kits for generating phage display libraries (e.g., the Pharmacia Recombinant Phage Antibody System, catalog no. 27-9400-01; and the Stratagene SurfZAP™ phage display kit, catalog no. 240612, the entire teachings of which are incorporated herein), examples of methods and reagents particularly amenable for use in generating and screening antibody display libraries can be found in, e.g., Ladner et al. U.S. Pat. No. 5,223,409; Kang et al. PCT Publication No. WO 92/18619; Dower et al. PCT Publication No. WO 91/17271; Winter et al. PCT Publication No. WO 92/20791; Markland et al. PCT Publication No. WO 92/15679; Breitling et al. PCT Publication No. WO 93/01288; McCafferty et al. PCT Publication No. WO 92/01047; Garrard et al. PCT Publication No. WO 92/09690; Fuchs et al. (1991) Bio/Technology 9:1370-1372; Hay et al. (1992) Hum Antibod Hybridomas 3:81-85; Huse et al. (1989) Science 246:1275-1281; McCafferty et al., Nature (1990) 348:552-554; Griffiths et al. (1993) EMBO J 12:725-734; Hawkins et al. (1992) J Mol Biol 226:889-896; Clackson et al. (1991) Nature 352:624-628; Gram et al. (1992) PNAS 89:3576-3580; Garrard et al. (1991) Bio/Technology 9:1373-1377; Hoogenboom et al. (1991) Nuc Acid Res 19:4133-4137; and Barbas et al. (1991) PNAS 88:7978-7982; the entire teachings of which are incorporated herein.

Human monoclonal antibodies of this disclosure can also be prepared using SCID mice into which human immune cells have been reconstituted such that a human antibody response can be generated upon immunization. Such mice are described in, for example, U.S. Pat. Nos. 5,476,996 and 5,698,767 to Wilson et al.

The antibodies or antigen-binding portions thereof, of this disclosure can be altered wherein the constant region of the antibody is modified to reduce at least one constant region-mediated biological effector function relative to an unmodified antibody. To modify an antibody of the invention such that it exhibits reduced binding to the Fc receptor, the immunoglobulin constant region segment of the antibody can be mutated at particular regions necessary for Fc receptor (FcR) interactions (see, e.g., Canfield and Morrison (1991) J. Exp. Med. 173:1483-1491; and Lund et al. (1991) J. of Immunol. 147:2657-2662, the entire teachings of which are incorporated herein). Reduction in FcR binding ability of the antibody may also reduce other effector functions which rely on FcR interactions, such as opsonization and phagocytosis and antigen-dependent cellular cytotoxicity.

4.3. Antibody Production

To express an antibody of the invention, DNAs encoding partial or full-length light and heavy chains are inserted into one or more expression vector such that the genes are operatively linked to transcriptional and translational control sequences. (See, e.g., U.S. Pat. No. 6,914,128, the entire teaching of which is incorporated herein by reference.) In this context, the term “operatively linked” is intended to mean that an antibody gene is ligated into a vector such that transcriptional and translational control sequences within the vector serve their intended function of regulating the transcription and translation of the antibody gene. The expression vector and expression control sequences are chosen to be compatible with the expression host cell used. The antibody light chain gene and the antibody heavy chain gene can be inserted into a separate vector or, more typically, both genes are inserted into the same expression vector. The antibody genes are inserted into an expression vector by standard methods (e.g., ligation of complementary restriction sites on the antibody gene fragment and vector, or blunt end ligation if no restriction sites are present). Prior to insertion of the antibody or antibody-related light or heavy chain sequences, the expression vector may already carry antibody constant region sequences. Additionally or alternatively, the recombinant expression vector can encode a signal peptide that facilitates secretion of the antibody chain from a host cell. The antibody chain gene can be cloned into the vector such that the signal peptide is linked in-frame to the amino terminus of the antibody chain gene. The signal peptide can be an immunoglobulin signal peptide or a heterologous signal peptide (i.e., a signal peptide from a non-immunoglobulin protein).

In addition to the antibody chain genes, a recombinant expression vector of the invention can carry one or more regulatory sequence that controls the expression of the antibody chain genes in a host cell. The term “regulatory sequence” is intended to include promoters, enhancers and other expression control elements (e.g., polyadenylation signals) that control the transcription or translation of the antibody chain genes. Such regulatory sequences are described, e.g., in Goeddel; Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif. (1990), the entire teaching of which is incorporated herein by reference. It will be appreciated by those skilled in the art that the design of the expression vector, including the selection of regulatory sequences may depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, etc. Suitable regulatory sequences for mammalian host cell expression include viral elements that direct high levels of protein expression in mammalian cells, such as promoters and/or enhancers derived from cytomegalovirus (CMV) (such as the CMV promoter/enhancer), Simian Virus 40 (SV40) (such as the SV40 promoter/enhancer), adenovirus, (e.g., the adenovirus major late promoter (AdMLP)) and polyoma. For further description of viral regulatory elements, and sequences thereof, see, e.g., U.S. Pat. No. 5,168,062 by Stinski, U.S. Pat. No. 4,510,245 by Bell et al. and U.S. Pat. No. 4,968,615 by Schaffner et al., the entire teachings of which are incorporated herein by reference.

In addition to the antibody chain genes and regulatory sequences, a recombinant expression vector of the invention may carry one or more additional sequences, such as a sequence that regulates replication of the vector in host cells (e.g., origins of replication) and/or a selectable marker gene. The selectable marker gene facilitates selection of host cells into which the vector has been introduced (see e.g., U.S. Pat. Nos. 4,399,216, 4,634,665 and 5,179,017, all by Axel et al., the entire teachings of which are incorporated herein by reference). For example, typically the selectable marker gene confers resistance to drugs, such as G418, hygromycin or methotrexate, on a host cell into which the vector has been introduced. Suitable selectable marker genes include the dihydrofolate reductase (DHFR) gene (for use in dhfr- host cells with methotrexate selection/amplification) and the neo gene (for G418 selection).

An antibody of the invention can be prepared by recombinant expression of immunoglobulin light and heavy chain genes in a host cell. To express an antibody recombinantly, a host cell is transfected with one or more recombinant expression vectors carrying DNA fragments encoding the immunoglobulin light and heavy chains of the antibody such that the light and heavy chains are expressed in the host cell and secreted into the medium in which the host cells are cultured, from which medium the antibodies can be recovered. Standard recombinant DNA methodologies are used to obtain antibody heavy and light chain genes, incorporate these genes into recombinant expression vectors and introduce the vectors into host cells, such as those described in Sambrook, Fritsch and Maniatis (eds), Molecular Cloning; A Laboratory Manual, Second Edition, Cold Spring Harbor, N.Y., (1989), Ausubel et al. (eds.) Current Protocols in Molecular Biology, Greene Publishing Associates, (1989) and in U.S. Pat. Nos. 4,816,397 & 6,914,128, the entire teachings of which are incorporated herein.

For expression of the light and heavy chains, the expression vector(s) encoding the heavy and light chains is (are) transfected into a host cell by standard techniques. The various forms of the term “transfection” are intended to encompass a wide variety of techniques commonly used for the introduction of exogenous DNA into a prokaryotic or eukaryotic host cell, e.g., electroporation, calcium-phosphate precipitation, DEAE-dextran transfection and the like. Although it is theoretically possible to express the antibodies of the invention in either prokaryotic or eukaryotic host cells, expression of antibodies in eukaryotic cells, such as mammalian host cells, is suitable because such eukaryotic cells, and in particular mammalian cells, are more likely than prokaryotic cells to assemble and secrete a properly folded and immunologically active antibody. Prokaryotic expression of antibody genes has been reported to be ineffective for production of high yields of active antibody (Boss and Wood (1985) Immunology Today 6:12-13, the entire teaching of which is incorporated herein by reference).

Suitable host cells for cloning or expressing the DNA in the vectors herein are the prokaryote, yeast, or higher eukaryote cells described above. Suitable prokaryotes for this purpose include eubacteria, such as Gram-negative or Gram-positive organisms, e.g., Enterobacteriaceae such as Escherichia, e.g., E. coli, Enterobacter, Erwinia, Klebsiella, Proteus, Salmonella, e.g., Salmonella typhimurium, Serratia, e.g., Serratia marcescans, and Shigella, as well as Bacilli such as B. subtilis and B. licheniformis (e.g., B. licheniformis 41P disclosed in DD 266,710 published Apr. 12, 1989), Pseudomonas such as P. aeruginosa, and Streptomyces. One suitable E. coli cloning host is E. coli 294 (ATCC 31,446), although other strains such as E. coli B, E. coli X1776 (ATCC 31,537), and E. coli W3110 (ATCC 27,325) are suitable. These examples are illustrative rather than limiting.

In addition to prokaryotes, eukaryotic microbes such as filamentous fungi or yeast are suitable cloning or expression hosts for polypeptide encoding vectors. Saccharomyces cerevisiae, or common baker's yeast, is the most commonly used among lower eukaryotic host microorganisms. However, a number of other genera, species, and strains are commonly available and useful herein, such as Schizosaccharomyces pombe; Kluyveromyces hosts such as, e.g., K. lactis, K. fragilis (ATCC 12,424), K. bulgaricus (ATCC 16,045), K. wickeramii (ATCC 24,178), K. waltii (ATCC 56,500), K. drosophilarum (ATCC 36,906), K. thermotolerans, and K. marxianus; yarrowia (EP 402,226); Pichia pastoris (EP 183,070); Candida; Trichoderma reesia (EP 244,234); Neurospora crassa; Schwanniomyces such as Schwanniomyces occidentalis; and filamentous fungi such as, e.g., Neurospora, Penicillium, Tolypocladium, and Aspergillus hosts such as A. nidulans and A. niger.

Suitable host cells for the expression of glycosylated antibodies are derived from multicellular organisms. Examples of invertebrate cells include plant and insect cells. Numerous baculoviral strains and variants and corresponding permissive insect host cells from hosts such as Spodoptera frugiperda (caterpillar), Aedes aegypti (mosquito), Aedes albopictus (mosquito), Drosophila melanogaster (fruitfly), and Bombyx mori have been identified. A variety of viral strains for transfection are publicly available, e.g., the L-1 variant of Autographa californica NPV and the Bm-5 strain of Bombyx mori NPV, and such viruses may be used as the virus herein according to the present invention, particularly for transfection of Spodoptera frugiperda cells. Plant cell cultures of cotton, corn, potato, soybean, petunia, tomato, and tobacco can also be utilized as hosts.

Suitable mammalian host cells for expressing the recombinant antibodies of the invention include Chinese Hamster Ovary (CHO cells) (including dhfr- CHO cells, described in Urlaub and Chasin, (1980) PNAS USA 77:4216-4220, used with a DHFR selectable marker, e.g., as described in Kaufman and Sharp (1982) Mol. Biol. 159:601-621, the entire teachings of which are incorporated herein by reference), NSO myeloma cells, COS cells and SP2 cells. When recombinant expression vectors encoding antibody genes are introduced into mammalian host cells, the antibodies are produced by culturing the host cells for a period of time sufficient to allow for expression of the antibody in the host cells or secretion of the antibody into the culture medium in which the host cells are grown. Other examples of useful mammalian host cell lines are monkey kidney CV1 line transformed by SV40 (COS-7, ATCC CRL 1651); human embryonic kidney line (293 or 293 cells subcloned for growth in suspension culture, Graham et al., J. Gen Virol. 36:59 (1977)); baby hamster kidney cells (BHK, ATCC CCL 10); Chinese hamster ovary cells/-DHFR (CHO, Urlaub et al., Proc. Natl. Acad. Sci. USA 77:4216 (1980)); mouse sertoli cells (TM4, Mather, Biol. Reprod. 23:243-251 (1980)); monkey kidney cells (CV1 ATCC CCL 70); African green monkey kidney cells (VERO-76, ATCC CRL-1587); human cervical carcinoma cells (HELA, ATCC CCL 2); canine kidney cells (MDCK, ATCC CCL 34); buffalo rat liver cells (BRL 3A, ATCC CRL 1442); human lung cells (W138, ATCC CCL 75); human liver cells (Hep G2, HB 8065); mouse mammary tumor (MMT 060562, ATCC CCL51); TRI cells (Mather et al., Annals N.Y. Acad. Sci. 383:44-68 (1982)); MRC 5 cells; FS4 cells; and a human hepatoma line (Hep G2), the entire teachings of which are incorporated herein by reference.

Host cells are transformed with the above-described expression or cloning vectors for antibody production and cultured in conventional nutrient media modified as appropriate for inducing promoters, selecting transformants, or amplifying the genes encoding the desired sequences.

The host cells used to produce an antibody may be cultured in a variety of media. Commercially available media such as Ham's F10™ (Sigma), Minimal Essential Medium™ ((MEM), (Sigma), RPMI-1640 (Sigma), and Dulbecco's Modified Eagle's Medium™ ((DMEM), Sigma) are suitable for culturing the host cells. In addition, any of the media described in Ham et al., Meth. Enz. 58:44 (1979), Barnes et al., Anal. Biochem. 102:255 (1980), U.S. Pat. Nos. 4,767,704; 4,657,866; 4,927,762; 4,560,655; or 5,122,469; WO 90/03430; WO 87/00195; or U.S. Pat. No. Re. 30,985 may be used as culture media for the host cells, the entire teachings of which are incorporated herein by reference. Any of these media may be supplemented as necessary with hormones and/or other growth factors (such as insulin, transferrin, or epidermal growth factor), salts (such as sodium chloride, calcium, magnesium, and phosphate), buffers (such as HEPES), nucleotides (such as adenosine and thymidine), antibiotics (such as gentamycin drug), trace elements (defined as inorganic compounds usually present at final concentrations in the micromolar range), and glucose or an equivalent energy source. Any other necessary supplements may also be included at appropriate concentrations that would be known to those skilled in the art. The culture conditions, such as temperature, pH, and the like, are those previously used with the host cell selected for expression, and will be apparent to the ordinarily skilled artisan.

Host cells can also be used to produce portions of intact antibodies, such as Fab fragments or scFv molecules. It is understood that variations on the above procedure are within the scope of the present invention. For example, in certain embodiments it may be desirable to transfect a host cell with DNA encoding either the light chain or the heavy chain (but not both) of an antibody of this invention. Recombinant DNA technology may also be used to remove some or the entire DNA encoding either or both of the light and heavy chains that is not necessary for binding to the antigen to which the putative antibody of interest binds. The molecules expressed from such truncated DNA molecules are also encompassed by the antibodies of the invention. In addition, bifunctional antibodies may be produced in which one heavy and one light chain are an antibody of the invention and the other heavy and light chain are specific for an antigen other than the one to which the putative antibody of interest binds, depending on the specificity of the antibody of the invention, by crosslinking an antibody of the invention to a second antibody by standard chemical crosslinking methods.

In a suitable system for recombinant expression of an antibody of the invention, a recombinant expression vector encoding both the antibody heavy chain and the antibody light chain is introduced into dhfr-CHO cells by calcium phosphate-mediated transfection. Within the recombinant expression vector, the antibody heavy and light chain genes are each operatively linked to CMV enhancer/AdMLP promoter regulatory elements to drive high levels of transcription of the genes. The recombinant expression vector also carries a DHFR gene, which allows for selection of CHO cells that have been transfected with the vector using methotrexate selection/amplification. The selected transformant host cells are cultured to allow for expression of the antibody heavy and light chains and intact antibody is recovered from the culture medium. Standard molecular biology techniques are used to prepare the recombinant expression vector, transfect the host cells, select for transformants, culture the host cells and recover the antibody from the culture medium.

When using recombinant techniques, the antibody can be produced intracellularly, in the periplasmic space, or directly secreted into the medium. In one aspect, if the antibody is produced intracellularly, as a first step, the particulate debris, either host cells or lysed cells (e.g., resulting from homogenization), can be removed, e.g., by centrifugation or ultrafiltration. Where the antibody is secreted into the medium, supernatants from such expression systems can be first concentrated using a commercially available protein concentration filter, e.g., an Amicon™ or Millipore Pellicon™ ultrafiltration unit.

Prior to the process of the invention, procedures for purification of antibodies from cell debris initially depend on the site of expression of the antibody. Some antibodies can be secreted directly from the cell into the surrounding growth media; others are made intracellularly. For the latter antibodies, the first step of a purification process typically involves: lysis of the cell, which can be done by a variety of methods, including mechanical shear, osmotic shock, or enzymatic treatments. Such disruption releases the entire contents of the cell into the homogenate, and in addition produces subcellular fragments that are difficult to remove due to their small size. These are generally removed by differential centrifugation or by filtration. Where the antibody is secreted, supernatants from such expression systems are generally first concentrated using a commercially available protein concentration filter, e.g., an Amicon™ or Millipore Pellicon™ ultrafiltration unit. Where the antibody is secreted into the medium, the recombinant host cells can also be separated from the cell culture medium, e.g., by tangential flow filtration. Antibodies can be further recovered from the culture medium using the antibody purification methods of the invention.

4.4. Antibody Purification

4.4.1 Antibody Purification Generally

In certain embodiments, the invention provides methods and compositions for producing a purified or partially purified (e.g., process-related impurity-reduced and/or product-related substance-reduced) protein preparation from a mixture comprising a protein of interest, e.g., an antibody, and at least one process-related impurity or product-related substance. In certain embodiments, the compositions of the present invention include, but are not limited to, process-related impurity-reduced and/or product-related substance-reduced compositions comprising a protein of interest. Such process-related impurity-reduced and/or product-related substance-reduced compositions address the need for improved product characteristics, including, but not limited to, product stability, product safety and product efficacy.

In certain embodiments, the purification process of the invention begins at the separation step when the antibody has been produced using production methods described above and/or by alternative production methods conventional in the art. Once a clarified solution or mixture comprising the protein of interest, e.g., an antibody, has been obtained, separation of the protein of interest from process-related impurities, such as the other proteins produced by the cell, as well as any product-related substances such as charge variants and/or size variants (aggregates and fragments), can be performed. In certain non-limiting embodiments, such separation is performed using Protein A affinity chromatography followed by a displacement chromatographic step. In certain embodiments, a combination of one or more different purification techniques, including ion exchange separation step(s) and/or hydrophobic interaction separation step(s) can also be employed. Such additional purification steps separate mixtures of proteins on the basis of their charge, degree of hydrophobicity, and/or size. In one aspect of the invention, such additional separation steps are performed using chromatography, including hydrophobic, anionic or cationic, or mixed mode interaction. Several different chromatography resins are available for each of these techniques, allowing accurate tailoring of the purification scheme to the particular protein involved. The essence of each of the separation methods is that proteins can either traverse at different rates down a column, achieving a physical separation that increases as they pass further down the column, or to adhere selectively to the separation medium, being then differentially eluted by different solvents, or by the presence of a displacer (in the context of displacement chromatography). In some cases, the antibody is separated from impurities when the impurities specifically adhere to the column and the antibody does not, i.e., the antibody is present in the flow-through, while in other cases the antibody will adhere to the column, while the impurities flow-through.

4.4.2 Primary Recovery

In certain embodiments, the initial steps of the purification methods of the present invention involve the clarification and primary recovery of antibody from a sample matrix. In certain embodiments, the primary recovery will include one or more centrifugation steps to separate the antibody product from the cells and cell debris. Centrifugation of the sample can be run at, for example, but not by way of limitation, 7,000×g to approximately 12,750×g. In the context of large scale purification, such centrifugation can occur on-line with a flow rate set to achieve, for example, but not by way of limitation, a turbidity level of 150 NTU in the resulting supernatant. Such supernatant can then be collected for further purification, or in-line filtered through one or more depth filters for further clarification of the sample.

In certain embodiments, the primary recovery will include the use of one or more depth filtration steps to clarify the sample matrix and thereby aid in purifying the antibodies of interest in the present invention. In other embodiments, the primary recovery will include the use of one or more depth filtration steps post centrifugation to further clarify the sample matrix. Non-limiting examples of depth filters that can be used in the context of the instant invention include the Millistak+ XOHC, FOHC, DOHC, A1HC, B1HC depth filters (EMD Millipore), Cuno™ model 30/60ZA, 60/90 ZA, VR05, VR07, delipid depth filters (3M Corp.). A 0.2 μm filter such as Sartorius's 0.45/0.2 μm Sartopore™ bi-layer or Millipore's Express SHR or SHC filter cartridges typically follows the depth filters.

In certain embodiments, the primary recovery process can also be a point at which to reduce or inactivate viruses that can be present in the sample matrix. For example, any one or more of a variety of methods of viral reduction/inactivation can be used during the primary recovery phase of purification including heat inactivation (pasteurization), pH inactivation, solvent/detergent treatment, UV and γ-ray irradiation and the addition of certain chemical inactivating agents such as β-propiolactone or e.g., copper phenanthroline as in U.S. Pat. No. 4,534,972. In certain embodiments of the present invention, the sample matrix is exposed to detergent viral inactivation during the primary recovery phase. In other embodiments, the sample matrix may be exposed to low pH inactivation during the primary recovery phase.

In those embodiments where viral reduction/inactivation is employed, the sample mixture can be adjusted, as needed, for further purification steps. For example, following low pH viral inactivation, the pH of the sample mixture is typically adjusted to a more neutral pH, e.g., from about 4.5 to about 8.5, prior to continuing the purification process. Additionally, the mixture may be diluted with water for injection (WFI) to obtain a desired conductivity.

4.4.3 Protein A Affinity Chromatography

In certain embodiments, particularly where the protein of interest is an antibody, the primary recovery sample is subjected to Protein A affinity chromatography to substantially purify the antibody of interest away from HCPs. There are a variety of commercial sources for Protein A resin. Suitable resins include, but not limited to, MabSelect SuRe™, MabSelect SuRe LX, MabSelect, MabSelect Xtra, rProtein A Sepharose from GE Healthcare, ProSep HC, ProSep Ultra, and ProSep Ultra Plus from EMD Millipore, MapCapture from Life Technologies.

In certain embodiments, the Protein A column can be equilibrated with a suitable buffer prior to sample loading. Following the loading of the column, the column can be washed one or multiple times using a suitable sets of buffers. The Protein A column can then be eluted using an appropriate elution buffer. The eluate can be monitored using techniques well known to those skilled in the art. The eluate fractions of interest can be collected and then prepared for further processing.

The Protein A eluate may subject to a viral inactivation step either by detergent or low pH, provided this step is not performed prior to the Protein A capture operation. A proper detergent concentration or pH and time can be selected to obtain desired viral inactivation results. After viral inactivation, the Protein A eluate is usually pH and/or conductivity adjusted for subsequent purification steps.

The Protein A eluate may be subjected to filtration through a depth filter to remove turbidity and/or various impurities from the antibody of interest prior to additional chromatographic polishing steps. Examples of depth filters include, but not limited to, Millistak+ XOHC, FOHC, DOHC, A1HC, and B1HC Pod filters (EMD Millipore), or Zeta Plus 30ZA/60ZA, 60ZA/90ZA, delipid, VR07, and VRO5 filters (3M). The Protein A eluate pool may need to be conditioned to proper pH and conductivity to obtain desired impurity removal and product recovery from the depth filtration step.

4.4.4 Displacement Chromatography

In certain embodiments of the present invention, a sample, e.g., a primary recovery sample, a Protein A eluate sample, or a sample having undergone one or more of the purification strategies outlined herein, is subjected to displacement chromatography. In certain embodiments the displacer molecule is selected to have a higher affinity for the stationary phase (i.e., the chromatographic support) than the components present in the material to be separated. In certain embodiments, the displacer induces the components of the mixture to develop into consecutive zones of concentrated and purified species in the order of decreasing binding affinity ahead of the displacer front (a “displacement train”). In certain embodiments, the displacement process allows for higher column loading levels (as compared to conventional high-resolution chromatographic separations such as bind and linear gradient elution mode) without compromising the purity and recovery of the component of interest. In certain embodiments, washing of the displacement train from the column using the displacer solution allows for the component of interest to be isolated by collecting (and pooling if necessary) the proper fraction(s) of the displaced eluate. Along with acidic species, other product-related substances, such as basic species, product aggregates, and/or product fragments, and process-related impurities, such as HCPs, can be selectively collected or reduced.

In certain embodiments, the displacer will be employed in the context of an ion exchange or mixed mode chromatographic separation. A detailed description of ion exchange chromatography and a listing of exemplary chromatographic supports which can be employed in the context of displacement chromatography are presented in Section 4.4.5, below. A detailed description of mixed mode chromatography and a listing of exemplary chromatographic supports which can be employed in the context of displacement chromatography are presented in Section 4.4.6, below. In certain non-limiting embodiments, a cation exchange, an anion exchange, or a mixed mode displacement chromatography step is employed to effectively reduce product-related substances (e.g., acidic species and/or basic species such as Lys variants) from, e.g., a monoclonal antibody feed stream. In certain of such embodiments, conventional (or relatively weak) binding conditions can be employed and cationic molecules having high affinity for a CEX, AEX, or multimodal ligand (such as Expell SP1™ and protamine sulfate) can be employed to induce the formation of a product-related substances displacement train. In certain of such embodiments, the acidic population is enriched in the front followed by the main isoform, and, thereafter, the basic population. Thus, in certain embodiments, exclusion of those earlier fractions from the remainder eluate results in an AR-reduced product. Alternatively, exclusion of the fractions following the main isoform results in a Lys variant-reduced product. In certain embodiments, the fragments and aggregates are reduced in an AR-reduced product. In certain embodiments, the HCPs are reduced in an AR-reduced product.

In certain embodiments, the displacer concentration will be selected from the range of about 0.1 mM to about 10 mM, or about 0.25 mM to about 10 mM. In certain embodiments, the displacer concentration will be selected from a range of about 0.1 mM to about 5 mM, or about 0.25 mM to about 3 mM. In certain embodiments, the displacer concentration will be selected from a range of about 0.1 mM to about 5 mM, or about 0.25 mM to about 2 mM. In certain embodiments, the displacer concentration will be selected from a range of about 0.1 mM to about 2 mM, or about 0.25 mM to about 1 mM. In certain embodiments, the displacer concentration will be selected from a concentration of about 0.1 mM to about 1 mM, or about 0.25 mM to about 0.5 mM. In certain embodiments the displacer is Expell SP1™ and the displacer concentration will be selected from the range of about 0.1 mM to about 10 mM, or about 0.25 mM to about 10 mM. In certain embodiments, the displacer is protamine sulfate and the displacer concentration will be selected from the range of about 0.1 mM to about 5 mM, or about 0.25 mM to about 5 mM.

In certain embodiments, a displacing buffer was used in one-step displacement process. In certain embodiments, the total volume of the one-step displacing buffer is in the range of about 20 CVs to about 50 CVs, or about 25 CVs to about 40 CVs, or about 30 CVs.

Although displacement chromatography conventionally employs a displacer at a fixed concentration to achieve component separation, an improved method using multiple displacing buffers is disclosed herein. In certain embodiments, a two-step displacement method is employed where a first displacer concentration is employed for a certain initial number of column volumes (CVs) and a second, higher, displacer concentration is employed for a subsequent number of CVs. The total volume of the displacing buffers needed to complete the displacement process is significantly (e.g. 25-45%) less than that needed when using one displacing buffer in the one-step displacement process in order to achieve comparable separation performances. In certain embodiments the first displacer concentration is about 0.25 mM, about 0.35 mM, or about 0.5 mM. In certain embodiments, the second displacer concentration is about 0.5 mM, about 1 mM, about 2 mM, about 3 mM, about 4 mM, or about 5 mM.

In certain embodiments, a two-step displacement method is employed where the first displacer concentration is employed for up to about 10 CVs. In certain embodiments, the first displacer concentration is employed for up to about 25 CVs. In certain embodiments, the second displacer concentration is employed for up to about 10 CVs. In certain embodiments, the second displacer concentration is employed for up to about 25 CVs. In certain embodiments, the total required displacing buffer volume is about 13 CVs for a two-step displacement process. In certain embodiments, the total required displacer buffer volume is about 15 CVs for a two-step displacement process. In certain embodiments, the total required displacer buffer volume is about 33 CVs for a two-step displacement process. Once skilled in the art further reduction in required buffer volumes for each displacement step is expected. In certain embodiments, multiple steps of increasing displacer concentration are employed. As outlined in the Examples section, below, incorporation of additional displacement concentration steps into the purification strategy can allow for unexpectedly efficient charge variant, product aggregate, product fragment, and/or HCP clearance.

In certain embodiments, a linear gradient displacement method is employed where an initial, low, displacer concentration is followed by the addition of displacer at increasing concentrations in accordance with a linear gradient. For example, but not by way of limitation, the displacer concentration can range from about 0 mM to about 1 mM over the course of about 40 CVs. Again, as outlined in the Examples section, below, incorporation of a linear displacer concentration gradient into the purification strategy can allow for unexpectedly efficient charge variant, product aggregate, product fragment, and/or HCP clearance.

In certain embodiments, a displacement buffer consisting of two or more displacers is used. In certain embodiments, different displacers are used in the multi-step displacement process.

In certain embodiments of the present invention, the pH of the displacing wash buffer is below the pI of the protein of interest. In certain embodiments, the pH of the displacing wash buffer is in the range of about 5.0 to about 9.0, about 6.0 to about 8.0, about 7.0 to about 7.7, or about 7.5 to about 7.7. In certain embodiments of the present invention, the conductivity of the wash buffer is between about 1 to about 86 mS/cm, about 2 to about 20 mS/cm, about 2 to about 7 mS/cm, or about 5 to about 6.6 mS/cm. In certain embodiments of the present invention, the column bed height is between about 10 cm to about 30 cm, about 15 cm to about 25 cm, about 20 cm to about 30 cm, or about 25 cm. In certain embodiments of the present invention, the flow residence time is between about 2 minutes to about 25 minutes, about 5 minutes to about 20 minutes, about 10 minutes to about 20 minutes, or about 15 minutes to about 20 minutes.

In certain embodiments, the displacer buffer pH and displacer concentration can affect the displacement profile and, as a result, impact clearance of process-related impurities and/or product-related substances, such as charge variants, in unexpected ways. Thus, effective operating regimes with regard to the reduction of process-related impurities and/or product-related substances depend on the specific protein-resin-displacer system. For example, but not by way of limitation, when a feed stream containing Adalimumab is separated using displacement chromatography, significant AR reduction (AAR %) can be achieved using a displacing buffer with pH in the range of 6-8 with displacer concentration as low as 0.25-0.5 mM. In fact, as described in Section 5.2 below, the extent of Adalimumab AR reduction increases significantly as pH varies from 6.5 to 7.5, for example, over a 6% decrease in AR level can be achieved at pH 7.5 with a product yield ˜75%. In certain embodiments, as outlined in the Examples presented below, the total AR level (%) in Adalimumab product pool can be reduced by over 10% with an acceptable processing yield (≧75%) from a CEX displacement chromatography process, or 4-7% from a mixed mode displacement chromatography process. Similarly, for mAb X, FIG. 32 indicates that AAR % surprisingly increases from 3.3 to 6.5% as pH varies from 7 to 7.7 in a mixed mode displacement chromatography process.

In certain embodiments, conditions selected for reducing AR are also capable of reducing process-related impurities and/or other product-related substances. For example, but not by way of limitation, conditions selected for AR reduction are also capable of reducing process-related impurities, such as HCPs. In additional, non-limiting examples, conditions selected for AR reduction are also capable of reducing product-related impurities, such as aggregates and/or fragments.

In certain embodiments, displacement chromatography can be used as the sole method of purification of the protein of interest. In certain embodiments, displacement chromatography can be used in combination with other purification strategies, such as, but not limited to, the alternative techniques described herein, to reduce process-related impurities and/or other product-related substances.

In certain embodiments, fractions are collected during the displacement step and are combined (pooled) after appropriate analysis to provide a protein preparation, which is also referred to herein as a purified or partially-purified sample, that contains a desired level of the protein of interest and which can include one or more process-related impurities and/or other product-related substances. In certain embodiments, one or more process monitoring tools can be used in connection with the techniques described herein to facilitate the identification of an effective product pooling strategy. In certain embodiments, such monitoring can include on-line or in-line process monitoring. For example, but not by way of limitation, spectroscopy methods such as UV, NIR, FTIR, Fluorescence, and Raman may be used to monitor levels of product-related species, e.g., acidic species and lysine variants, in an on-line, at line or in-line mode. These methods allow for the production of data that can then be used to control the level of product-related species in the pooled material collected. In certain embodiments, specific signals arising from the chemical modification of the proteins such as glycation, MGO modification, deamidation, glycosylation may be specifically measurable by spectroscopic methods through such in-line, on-line or at-line methods, enabling real time or near-real time control of product quality of the resulting product.

In certain embodiments, the purification and/or pooling techniques described herein allow for the reduction of process-related impurities and/or other product-related substances. In certain embodiments, the purification and/or pooling techniques described herein allow for reduction of process-related impurities and the selective inclusion of particular product-related substances. For example, but not by way of limitation, the purification and/or pooling techniques described herein allow for modulation of the concentration of product-related substances in the purified sample, e.g., increasing or decreasing the amount of AR and/or basic species. In certain embodiments, the concentration of particular AR and/or basic species, e.g., Lys0, Lys1, and/or Lys2, are modulated (increased or decreased) in the purified sample. In certain embodiments, such techniques can be used to ensure product uniformity over the course of multiple production runs.

4.4.5 Ion Exchange Chromatography

In certain embodiments, the instant invention provides methods for producing process-related impurity and/or product-related substance-reduced protein preparation from a mixture comprising a protein of interest (i.e., a product) and at least one process-related impurity and/or product-related substance by subjecting the mixture to at least one ion exchange separation step. In certain embodiments, the ion exchange step will occur after the above-described Protein A affinity and/or displacement chromatography steps, such that an eluate comprising the protein of interest is obtained. Ion exchange separation includes any method by which two substances are separated based on the difference in their respective ionic charges, and can employ either cationic exchange material or anionic exchange material.

The use of a cationic exchange material versus an anionic exchange material can be based on the local charges of the protein at a given solution condition. Therefore, it is within the scope of this invention to employ an anionic exchange step prior to or subsequent to the use of a displacement chromatography step, or a cationic exchange step prior to or subsequent to the use of a displacement chromatography step.

In performing the separation, the initial protein mixture can be contacted with the ion exchange material by using any of a variety of techniques, e.g., using a batch purification technique or a chromatographic technique.

For example, in the context of batch purification, ion exchange material is prepared in, or equilibrated to, the desired starting buffer. Upon preparation, or equilibration, a slurry of the ion exchange material is obtained. The protein of interest, e.g., an antibody, solution is contacted with the slurry to adsorb the protein of interest to be separated to the ion exchange material. The solution comprising the process-related impurities and product-related substances that do not bind to the ion exchange material is separated from the slurry, e.g., by allowing the slurry to settle and removing the supernatant. The slurry can be subjected to one or more wash steps. If desired, the slurry can be contacted with a solution of higher conductivity to desorb process-related impurities and product-related substances that have bound to the ion exchange material. In order to elute bound polypeptides, the salt concentration of the buffer can be increased.

In the context of chromatographic separation, a chromatographic apparatus, commonly cylindrical in shape, is employed to contain the chromatographic support material (e.g., ion exchange material) prepared in an appropriate buffer solution. The chromatographic apparatus, if cylindrical, can have a diameter of about 5 mm to about 50 mm, and a height of 5 cm to 1 m, and in certain embodiments, particularly for large scale processing, a height of ≦30 cm is employed. Once the chromatographic material is added to the chromatographic apparatus, a sample containing the protein of interest, e.g., an antibody, is contacted to the chromatographic material to adsorb the protein of interest to be separated to the chromatographic material. The solution comprising the process-related impurities and product-related substances that do not bind to the chromatographic material is separated from the material by washing the materials and collecting fractions from the bottom of the column. The chromatographic material can be subjected to one or more wash steps. If desired, the chromatographic material can be contacted with a solution of higher conductivity to desorb process-related impurities and product-related substances that have bound to the chromatographic material. In order to elute bound polypeptides, the salt concentration of the buffer can be increased.

Ion exchange chromatography separates molecules based on differences between the local charges of the proteins of interest and the local charges of the chromatographic material. A packed ion-exchange chromatography column or an ion-exchange membrane device can be operated either in bind-elute mode or flow-through mode. In the bind-elute mode, the column or the membrane device is first conditioned with a buffer with low ionic strength and proper pH under which the protein carries sufficient local opposite charge to the local charge of the material immobilized on the resin based matrix. During the feed load, the protein of interest will be adsorbed to the resin due to electrostatic attraction. After washing the column or the membrane device with the equilibration buffer or another buffer with different pH and/or conductivity, the product recovery is achieved by increasing the ionic strength (i.e., conductivity) of the elution buffer to compete with the solute for the charged sites of the ion exchange matrix. Changing the pH and thereby altering the charge of the solute is another way to achieve elution of the solute. The change in conductivity or pH may be gradual (gradient elution) or stepwise (step elution). In the flow-through mode, the column or the membrane device is operated at selected pH and conductivity such that the protein of interest does not bind to the resin or the membrane while the process-related impurities and/or product-related substances will be retained to the column or the membrane. The column is then regenerated before next use.

Anionic or cationic substituents may be attached to matrices in order to form anionic or cationic supports for chromatography. Non-limiting examples of anionic exchange substituents include diethylaminoethyl (DEAE), quaternary aminoethyl (QAE) and quaternary amine (Q) groups. Cationic substitutents include carboxymethyl (CM), sulfoethyl (SE), sulfopropyl (SP), phosphate (P) and sulfonate (S). Cellulose ion exchange resins such as DE23™, DE32™, DE52™, CM-23™, CM-32™, and CM-52™ are available from Whatman Ltd. Maidstone, Kent, U.K. SEPHADEX®-based and -locross-linked ion exchangers are also known. For example, DEAE-, QAE-, CM-, and SP- SEPHADEX® and DEAE-, Q-, CM- and 5-SEPHAROSE® and SEPHAROSE® Fast Flow, and Capto™ S are all available from GE Healthcare. Further, both DEAE and CM derivitized ethylene glycol-methacrylate copolymer such as TOYOPEARL™ DEAE-650S or M and TOYOPEARL™ CM-650S or M are available from Toso Haas Co., Philadelphia, Pa., or Nuvia S and UNOSphere™ S from BioRad, Hercules, Calif., Eshmuno® S from EMD Millipore, Billerica, Calif.

This ion exchange step facilitates the purification of the antibody of interest by reducing impurities such as HCPs, DNA and aggregates. In certain aspects, the ion exchange column is an anion exchange column. For example, but not by way of limitation, a suitable resin for such an anion exchange column is Capto™ Q, Nuvia™ Q, Q Sepharose Fast Flow, and Poros HQ 50. These resins are available from commercial sources such as GE Healthcare, BioRad, or Life Technologies. This anion exchange chromatography process can be carried out at or around room temperature.

4.4.6 Mixed Mode Chromatography

Mixed mode chromatography, also referred to herein as “multimodal chromatography”, is a chromatographic strategy that utilizes a support comprising a ligand that is capable of providing at least two different, in certain embodiments co-operative, sites that interact with the substance to be bound. In certain embodiments, one of these sites gives an attractive type of charge-charge interaction between the ligand and the substance of interest and the other site provides for electron acceptor-donor interaction and/or hydrophobic and/or hydrophilic interactions. Electron donor-acceptor interactions include interactions such as hydrogen-bonding, π-π, cation-π, charge transfer, dipole-dipole, induced dipole etc. Mixed mode chromatographic supports include, but are not limited to, Nuvia C Prime, Toyo Pearl MX Trp 650M, and Eshmuno® HCX.

In certain embodiments, the mixed mode chromatography resin is comprised of ligands coupled to an organic or inorganic support, sometimes denoted a base matrix, directly or via a spacer. The support may be in the form of particles, such as essentially spherical particles, a monolith, filter, membrane, surface, capillaries, etc. In certain embodiments, the support is prepared from a native polymer, such as cross-linked carbohydrate material, such as agarose, agar, cellulose, dextran, chitosan, konjac, carrageenan, gellan, alginate etc. To obtain high adsorption capacities, the support can be porous, and ligands are then coupled to the external surfaces as well as to the pore surfaces. Such native polymer supports can be prepared according to standard methods, such as inverse suspension gelation (S Hjerten: Biochim Biophys Acta 79(2), 393-398 (1964). Alternatively, the support can be prepared from a synthetic polymer, such as cross-linked synthetic polymers, e.g. styrene or styrene derivatives, divinylbenzene, acrylamides, acrylate esters, methacrylate esters, vinyl esters, vinyl amides etc. Such synthetic polymers can be produced according to standard methods, see e.g. “Styrene based polymer supports developed by suspension polymerization” (R Arshady: Chimica e L′Industria 70(9), 70-75 (1988)). Porous native or synthetic polymer supports are also available from commercial sources, such as Amersham Biosciences, Uppsala, Sweden.

4.4.7 Hydrophobic Interaction Chromatography

The present invention also features methods for producing a process-related impurity and/or product-related substance-reduced protein preparation from a mixture comprising a protein of interest, e.g., an antibody, and at least one process-related impurity and/or product-related substance further comprising a hydrophobic interaction chromatography (HIC) step in addition to the displacement chromatography step.

In performing the separation, the sample mixture is contacted with the HIC material, e.g., using a batch purification technique or using a column or membrane chromatography. Prior to HIC purification it may be desirable to adjust the concentration of the kosmotropic salt to achieve desired protein binding to the resin or the membrane.

Whereas ion exchange chromatography relies on the local charge of the protein of interest for selective separation, hydrophobic interaction chromatography employs the hydrophobic properties of the proteins to achieve selective separation. Hydrophobic groups on the protein interact with hydrophobic groups of the resin or the membrane. The more hydrophobic a protein is the stronger it will interact with the column or the membrane. Thus the HIC step removes process-related impurities (e.g., HCPs) as well as product-related substances (e.g., aggregates and fragments).

Like ion exchange chromatography, a HIC column or membrane device can also be operated in product a bind-elute mode, a flow-through, or a hybrid mode wherein the product exhibits reversible binding to the chromatographic material. The bind-elute mode of operation has been explained above. For flow-through, the protein sample typically contains a relatively low level of salt than that used in the bind-elute mode. During this loading process, process-related impurities and product-related substances will bind to the resin while product flows through the column. After loading, the column is regenerated with water and cleaned with caustic solution to remove the bound impurities before next use. When used in connection with a hybrid mode, the product can be immobilized on the chromatographic support in the presence of a loading buffer, but can be removed by successive washes of buffer identical to or substantially similar to the loading buffer. During this process, process-related impurities and product-relates substances will either bind to the chromatographic material or flow through with a profile distinct from the protein of interest.

As hydrophobic interactions are strongest at high ionic strength, this form of separation is conveniently performed following salt elution step, such as those that are typically used in connection with ion exchange chromatography. Alternatively, salts can be added into a low salt level feed stream before this step. Adsorption of the antibody to a HIC column is favored by high salt concentrations, but the actual concentrations can vary over a wide range depending on the nature of the protein of interest, salt type and the particular HIC ligand chosen. Various ions can be arranged in a so-called soluphobic series depending on whether they promote hydrophobic interactions (salting-out effects) or disrupt the structure of water (chaotropic effect) and lead to the weakening of the hydrophobic interaction. Cations are ranked in terms of increasing salting out effect as Ba²⁺; Ca²⁺; Mg²⁺; Li⁺; Cs⁺; Na⁺; K⁺; Rb⁺; NH₄ ⁺, while anions may be ranked in terms of increasing chaotropic effect as PO₄ ³⁻; SO₄ ²⁻; CH₃CO₃ ⁻; Cl⁻; Br⁻; NO₃ ⁻; ClO₄ ⁻; I⁻; SCN⁻.

In general, Na⁺, K⁺ or NH₄ ⁺ sulfates effectively promote ligand-protein interaction in HIC. Salts may be formulated that influence the strength of the interaction as given by the following relationship: (NH₄)₂SO₄>Na₂SO₄>NaCl >NH₄Cl>NaBr>NaSCN. In general, salt concentrations of between about 0.75 M and about 2 M ammonium sulfate or between about 1 and 4 M NaCl are useful.

HIC media normally comprise a base matrix (e.g., cross-linked agarose or synthetic copolymer material) to which hydrophobic ligands (e.g., alkyl or aryl groups) are coupled. A suitable HIC media comprises an agarose resin or a membrane functionalized with phenyl groups (e.g., a Phenyl Sepharose™ from GE Healthcare or a Phenyl Membrane from Sartorius). Many HIC resins are available commercially. Examples include, but are not limited to, Capto Phenyl, Phenyl Sepharose™ 6 Fast Flow with low or high substitution, Phenyl Sepharose™ High Performance, Octyl Sepharose™ High Performance (GE Healthcare); Fractogel™ EMD Propyl or Fractogel™ EMD Phenyl (E. Merck, Germany); Macro-Prep™ Mehyl or Macro-Prep™ t-Butyl columns (Bio-Rad, California); WP HI-Propyl (C3)™ (J. T. Baker, New Jersey); and Toyopearl™ ether, phenyl or butyl (TosoHaas, Pa.).

4.4.8 Viral Filtration

Viral filtration is a dedicated viral reduction step in the entire purification process. This step is usually performed post chromatographic polishing steps. Viral reduction can be achieved via the use of suitable filters including, but not limited to, Planova 2ON™, 50 N or BioEx from Asahi Kasei Pharma, Viresolve™ filters from EMD Millipore, ViroSart CPV from Sartorius, or Ultipor DV20 or DV50™ filter from Pall Corporation. It will be apparent to one of ordinary skill in the art to select a suitable filter to obtain desired filtration performance.

4.4.9 Ultrafiltration/Diafiltration

Certain embodiments of the present invention employ ultrafiltration and diafiltration steps to further concentrate and formulate the protein of interest, e.g., an antibody product. Ultrafiltration is described in detail in: Microfiltration and Ultrafiltration: Principles and Applications, L. Zeman and A. Zydney (Marcel Dekker, Inc., New York, N.Y., 1996); and in: Ultrafiltration Handbook, Munir Cheryan (Technomic Publishing, 1986; ISBN No. 87762-456-9). One filtration process is Tangential Flow Filtration as described in the Millipore catalogue entitled “Pharmaceutical Process Filtration Catalogue” pp. 177-202 (Bedford, Mass., 1995/96). In contrast, diafiltration is a method of using membrane filters to remove and exchange salts, sugars, and non-aqueous solvents, to separate free from bound species, to remove low molecular-weight species, and/or to cause the rapid change of ionic and/or pH environments. Examples of membrane cassettes suitable for the present invention include, but not limited to, Pellicon 2 or Pellicon 3 cassetts with 10 kD, 30 kD or 50 kD membranes from EMD Millipore, Kvick 10 kD, 30 kD or 50 kD membrane cassettes from GE Healthcare, and Centramate or Centrasette 10 kD, 30 kD or 50 kD cassettes from Pall Corporation.

4.5. Methods of Assaying Sample Purity

4.5.1 Assaying Host Cell Protein

The present invention also provides methods for determining the residual levels of host cell protein (HCP) concentration in the isolated/purified antibody composition. As described above, HCPs are desirably excluded from the final target substance product. Exemplary HCPs include proteins originating from the source of the antibody production. Failure to identify and sufficiently remove HCPs from the target antibody may lead to reduced efficacy and/or adverse subject reactions.

As used herein, the term “HCP ELISA” refers to an ELISA where the second antibody used in the assay is specific to the HCPs produced from cells, e.g., CHO cells, used to generate the antibody of interest. The second antibody may be produced according to conventional methods known to those of skill in the art. For example, the second antibody may be produced using HCPs obtained by sham production and purification runs, i.e., the same cell line used to produce the antibody of interest is used, but the cell line is not transfected with antibody DNA. In an exemplary embodiment, the second antibody is produced using HCPs similar to those expressed in the cell expression system of choice, i.e., the cell expression system used to produce the target antibody.

Generally, HCP ELISA comprises sandwiching a liquid sample comprising HCPs between two layers of antibodies, i.e., a first antibody and a second antibody. The sample is incubated during which time the HCPs in the sample are captured by the first antibody, for example, but not limited to goat anti-CHO, affinity purified (Cygnus). A labeled second antibody, or blend of antibodies, specific to the HCPs produced from the cells used to generate the antibody, e.g., anti-CHO HCP Biotinylated, is added, and binds to the HCPs within the sample. In certain embodiments the first and second antibodies are polyclonal antibodies. In certain aspects the first and second antibodies are blends of polyclonal antibodies raised against HCPs. The amount of HCP contained in the sample is determined using the appropriate test based on the label of the second antibody.

HCP ELISA may be used for determining the level of HCPs in an antibody composition, such as an eluate, displacement samples or flow-through fractions obtained using the process described above. The present invention also provides a composition comprising an antibody, wherein the composition has less than 100 ng/mgHCPs as determined by an HCP Enzyme Linked Immunosorbent Assay (“ELISA”).

4.5.2 Assaying Charge and Size Variants

In certain embodiments, the levels of product-related substances, such as acidic species and other charge variants, in the chromatographic samples produced using the techniques described herein are analyzed. In certain embodiments a CEX-HPLC method is employed. For example, but not by way of limitation, a 4 mm×250 mm analytical Dionex ProPac WCX-10 column (Dionex, CA) can be used along with a Shimazhu HPLC system. In certain embodiments, the mobile phases employed in such an assay will include a 10 mM Sodium Phosphate dibasic pH 7.5 buffer (Mobile phase A) and a 10 mM Sodium Phosphate dibasic, 500 mM Sodium Chloride pH 5.5 buffer (Mobile phase B). In certain embodiments, the mobile phases can include a 20 mM MES, pH 6.5 buffer (Mobile phase A) and a 20 mM MES, 500 mM NaCl, pH 6.5 buffer (Mobile phase B). In certain embodiments, the mobile phases can include a 20 mM MES, pH 6.2 buffer (Mobile phase A) and a 20 mM MES, 250 mM NaCl, pH 6.2 buffer (Mobile phase B). In certain embodiments, a binary gradient, for example, but not by way of limitation, a 6% B: 0 min; 6-16% B: 0-20 min; 16-100%B: 20-22 min; 100% B: 22-26 min; 100-6% B: 26-28 min; 6% B: 28-35 min gradient can be used with detection at 280 nm. In certain, non-limiting embodiments, a binary gradient comprising 10% B: 0 min; 10-28% B: 1-46 min; 28-100% B: 46-47 min; 100% B: 47-52 min; 100-10% B: 52-53 min; 10% B: 53-58 min, will be used with detection at 280 nm. In certain embodiments, a binary gradient such as a 1% B: 0-1 min; 1-25% B: 1-46 min; 25-100% B: 46-47 min; 100% B: 47-52 min; 100-1% B: 52-53 min; 1% B: 53-60 min gradient can be used with detection at 280 nm. Quantitation can be based on the relative area percentage of detected peaks. In certain embodiments, the peaks that elute at residence time less than ˜7 min will represent the acidic peaks or AR region. In certain embodiments, all peaks eluting prior to the Main Isoform peak can be summed as the acidic region, and all peaks eluting after the Main peak can be summed as the basic region. In certain embodiments, all peaks eluting prior to the Main Isoform peak (but after, e.g., a 2 min retention time) were summed as the acidic region, and all peaks eluting after the Main peak were summed as the basic region.

In certain embodiments, the levels of aggregates, monomer, and fragments in the chromatographic samples produced using the techniques described herein are analyzed. In certain embodiments, the aggregates, monomer, and fragments are measured using a size exclusion chromatographic (SEC) method for each molecule. For example, but not by way of limitation, a TSK-gel G3000SWxL, 5 μm, 125 Å, 7.8×300 mm column (Tosoh Bioscience) can be used in connection with certain embodiments, while a TSK-gel Super SW3000, 4 μm, 250 Å, 4.6×300 mm column (Tosoh Bioscience) can be used in alternative embodiments. In certain embodiments, the aforementioned columns are used along with an Agilent or a Shimazhu HPLC system. In certain embodiments, sample injections are made under isocratic elution conditions using a mobile phase consisting of, for example, 100 mM sodium sulfate and 100 mM sodium phosphate at pH 6.8, and detected with UV absorbance at 214 nm. In certain embodiments, the mobile phase will consist of 1×PBS at pH 7.4, and elution profile detected with UV absorbance at 280 nm. In certain embodiments, quantification is based on the relative area of detected peaks.

4.6. Further Modifications

The purified proteins, e.g., antibodies, of the present invention can be modified. In some embodiments, the antibodies are chemically modified to provide a desired effect. For example, but not by way of limitation, pegylation of antibodies or antibody fragments of the invention may be carried out by any of the pegylation reactions known in the art, as described, e.g., in the following references: Focus on Growth Factors 3:4-10 (1992); EP 0 154 316; and EP 0 401 384, each of which is incorporated by reference herein in its entirety. In one aspect, the pegylation is carried out via an acylation reaction or an alkylation reaction with a reactive polyethylene glycol molecule (or an analogous reactive water-soluble polymer). A suitable water-soluble polymer for pegylation of the antibodies and antibody fragments of the invention is polyethylene glycol (PEG). As used herein, “polyethylene glycol” is meant to encompass any of the forms of PEG that have been used to derivatize other proteins, such as mono (Cl-ClO) alkoxy- or aryloxy-polyethylene glycol.

Methods for preparing pegylated antibodies and antibody fragments of the invention will generally comprise the steps of (a) reacting the antibody or antibody fragment with polyethylene glycol, such as a reactive ester or aldehyde derivative of PEG, under suitable conditions whereby the antibody or antibody fragment becomes attached to one or more PEG groups, and (b) obtaining the reaction products. It will be apparent to one of ordinary skill in the art to select the optimal reaction conditions or the acylation reactions based on known parameters and the desired result.

Generally the pegylated antibodies and antibody fragments have increased half-life, as compared to the nonpegylated antibodies and antibody fragments. The pegylated antibodies and antibody fragments may be employed alone, together, or in combination with other pharmaceutical compositions.

An antibody of the invention can be derivatized or linked to another functional molecule (e.g., another peptide or protein or a small molecule). For example, an antibody of the invention can be functionally linked (by chemical coupling, genetic fusion, noncovalent association or otherwise) to one or more other molecular entities, such as another antibody (e.g., a bispecific antibody or a diabody), a detectable agent, a cytotoxic agent, a pharmaceutical agent, and/or a protein or peptide that can mediate associate of the antibody with another molecule (such as a streptavidin core region or a polyhistidine tag) or can modulate the potency and/or efficacy of the targeted therapy (e.g. an antibody drug conjugate).

One type of derivatized antibody is produced by crosslinking two or more antibodies (of the same type or of different types, e.g., to create bispecific antibodies). Suitable crosslinkers include those that are heterobifunctional, having two distinctly reactive groups separated by an appropriate spacer (e.g., m-maleimidobenzoyl-N-hydroxysuccinimide ester) or homobifunctional (e.g., disuccinimidyl suberate). Such linkers are available from Pierce Chemical Company, Rockford, Ill.

Useful detectable agents with which an antibody of the invention may be derivatized include fluorescent compounds. Exemplary fluorescent detectable agents include fluorescein, fluorescein isothiocyanate, rhodamine, 5-dimethylamine-1-napthalenesulfonyl chloride, phycoerythrin and the like. An antibody may also be derivatized with detectable enzymes, such as alkaline phosphatase, horseradish peroxidase, glucose oxidase and the like. When an antibody is derivatized with a detectable enzyme, it is detected by adding additional reagents that the enzyme uses to produce a detectable reaction product. For example, when the detectable agent horseradish peroxidase is present, the addition of hydrogen peroxide and diaminobenzidine leads to a colored reaction product, which is detectable. An antibody may also be derivatized with biotin, and detected through indirect measurement of avidin or streptavidin binding.

4.7. Pharmaceutical Compositions

The proteins of interest, e.g., antibodies and antibody-binding portions thereof, of the invention can be incorporated into pharmaceutical compositions suitable for administration to a subject. In certain embodiments, the pharmaceutical composition comprises an antibody of the invention and a pharmaceutically acceptable carrier. As used herein, “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like that are physiologically compatible. Examples of pharmaceutically acceptable carriers include one or more of water, saline, phosphate buffered saline, dextrose, glycerol, ethanol and the like, as well as combinations thereof. In many cases, it is desirable to include isotonic agents, e.g., sugars, polyalcohols such as mannitol, sorbitol, or sodium chloride in the composition. Pharmaceutically acceptable carriers may further comprise minor amounts of auxiliary substances such as wetting or emulsifying agents, preservatives or buffers, which enhance the shelf life or effectiveness of the antibody.

The antibodies and antibody-binding portions thereof, of the invention can be incorporated into a pharmaceutical composition suitable for parenteral administration. The antibody or antibody-portions can be prepared as an injectable solution containing, e.g., 0.1-250 mg/mL antibody. The injectable solution can be composed of either a liquid or lyophilized dosage form in a flint or amber vial, ampule or pre-filled syringe. The buffer can be L-histidine approximately 1-50 mM, (optimally 5-10 mM), at pH 5.0 to 7.0 (optimally pH 6.0). Other suitable buffers include but are not limited to sodium succinate, sodium citrate, sodium phosphate or potassium phosphate. Sodium chloride can be used to modify the toxicity of the solution at a concentration of 0-300 mM (optimally 150 mM for a liquid dosage form). Cryoprotectants can be included for a lyophilized dosage form, principally 0-10% sucrose (optimally 0.5-1.0%). Other suitable cryoprotectants include trehalose and lactose. Bulking agents can be included for a lyophilized dosage form, principally 1-10% mannitol (optimally 24%). Stabilizers can be used in both liquid and lyophilized dosage forms, principally 1-50 mM L-methionine (optimally 5-10 mM). Other suitable bulking agents include glycine, arginine, can be included as 0-0.05% polysorbate-80 (optimally 0.005-0.01%). Additional surfactants include but are not limited to polysorbate 20 and BRIJ surfactants.

In one aspect, the pharmaceutical composition includes the antibody at a dosage of about 0.01 mg/kg-10 mg/kg. In another aspect, the dosages of the antibody include approximately 1 mg/kg administered every other week, or approximately 0.3 mg/kg administered weekly. A skilled practitioner can ascertain the proper dosage and regime for administering to a subject.

The compositions of this invention may be in a variety of forms. These include, e.g., liquid, semi-solid and solid dosage forms, such as liquid solutions (e.g., injectable and infusible solutions), dispersions or suspensions, tablets, pills, powders, liposomes and suppositories. The form depends on, e.g., the intended mode of administration and therapeutic application. Typical compositions are in the form of injectable or infusible solutions, such as compositions similar to those used for passive immunization of humans with other antibodies. One mode of administration is parenteral (e.g., intravenous, subcutaneous, intraperitoneal, intramuscular). In one aspect, the antibody is administered by intravenous infusion or injection. In another aspect, the antibody is administered by intramuscular or subcutaneous injection.

Therapeutic compositions typically must be sterile and stable under the conditions of manufacture and storage. The composition can be formulated as a solution, microemulsion, dispersion, liposome, or other ordered structure suitable to high drug concentration. Sterile injectable solutions can be prepared by incorporating the active compound (i.e., antibody) in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the active compound into a sterile vehicle that contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile, lyophilized powders for the preparation of sterile injectable solutions, the methods of preparation are vacuum drying and spray-drying that yields a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof. The proper fluidity of a solution can be maintained, e.g., by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. Prolonged absorption of injectable compositions can be brought about by including in the composition an agent that delays absorption, e.g., monostearate salts and gelatin.

The antibodies and antibody-binding portions thereof, of the present invention can be administered by a variety of methods known in the art, one route/mode of administration is subcutaneous injection, intravenous injection or infusion. As will be appreciated by the skilled artisan, the route and/or mode of administration will vary depending upon the desired results. In certain embodiments, the active compound may be prepared with a carrier that will protect the compound against rapid release, such as a controlled release formulation, including implants, transdermal patches, and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Many methods for the preparation of such formulations are patented or generally known to those skilled in the art. See, e.g., Sustained and Controlled Release Drug Delivery Systems, J. R. Robinson, ed., Marcel Dekker, Inc., New York, 1978, the entire teaching of which is incorporated herein by reference.

In certain aspects, an antibody or antibody-binding portion thereof, of the invention may be orally administered, e.g., with an inert diluent or an assimilable edible carrier. The compound (and other ingredients, if desired) may also be enclosed in a hard or soft shell gelatin capsule, compressed into tablets, or incorporated directly into the subject's diet. For oral therapeutic administration, the compounds may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. To administer a compound of the invention by other than parenteral administration, it may be necessary to coat the compound with, or co-administer the compound with, a material to prevent its inactivation.

Supplementary active compounds can also be incorporated into the compositions. In certain aspects, an antibody or antibody-binding portion thereof, of the invention is co-formulated with and/or co-administered with one or more additional therapeutic agents that are useful for treating disorders. Such combination therapies may advantageously utilize lower dosages of the administered therapeutic agents, thus avoiding possible toxicities or complications associated with the various monotherapies. It will be appreciated by the skilled practitioner that when the antibodies of the invention are used as part of a combination therapy, a lower dosage of antibody may be desirable than when the antibody alone is administered to a subject (e.g., a synergistic therapeutic effect may be achieved through the use of combination therapy which, in turn, permits use of a lower dose of the antibody to achieve the desired therapeutic effect).

It should be understood that the antibodies of the invention can be used alone or in combination with an additional agent, e.g., a therapeutic agent, said additional agent being selected by the skilled artisan for its intended purpose. For example, the additional agent can be a therapeutic agent art-recognized as being useful to treat the disease or condition being treated by the antibody of the present invention. The additional agent also can be an agent which imparts a beneficial attribute to the therapeutic composition, e.g., an agent which affects the viscosity of the composition.

5. EXAMPLES

Three antibodies were used in connection with the studies outlined below (Sections 5.1 - 5.8). Adalimumab antibody was generated from cell culture processed using chemical defined medium (CDM) and purified by a 4.4 cm (id.)×˜20 cm (L) MabSelect SuRe Protein A column. mAb X bulk drug substance was obtained from a three-step large scale purification process. mAb Y antibody was generated from a large scale manufacturing process and purified by a MabSelect SuRe Protein A column. Adalimumab Protein A eluate was in a buffer of ˜20 mM acetic acid at pH ˜4.2. The mAb X was in a buffer containing ˜15 mM histidine, pH ˜6. The mAb Y was in a buffer containing ˜10 mM sodium formate, pH ˜4.2. Each mAb feed was conditioned to the targeted pH, conductivity and concentration prior to the displacement chromatography experiment.

The cationic displacers, Expell SP1™ and protamine sulfate (from salmon sperm), were purchased from SACHEM Chemical Company and Sigma Aldrich, respectively.

Poros XS CEX resin (Life Technologies) was packed in a 0.66 cm×˜25 cm column. The column was equilibrated with a 140 mM Tris/Acetate buffer or a 30 mM MES, 10 mM NaCl buffer at the targeted pH and conductivity (Table 1). After equilibration, the column was loaded with each pre-conditioned feed at a resin loading level of ˜40 g/L followed by a 2 CV of equilibration buffer wash. The displacing buffer, which consists of defined concentration of Expell SP1™ or protamine sulfate in the equilibration buffer, was flowed through the column to initiate the displacement process. In standard one-step displacement wash process, this step was continued for at least 30 CV at a flow rate corresponding to 15 to 22 min residence time (RT) before column regeneration and cleaning with a caustic solution consisting of 0.5 N NaOH and 0.5 M KCl. Alternatively, the displacement wash step comprised two displacement buffers each flowing for defined volumes, or a linear gradient flow from low to high concentration displacer buffer. Sample fractions were collected at every 0.5 or 1 CV for protein concentration and quality analysis. The specific processing conditions are detailed in Tables 1 and 2.

Capto MMC resin (GE Healthcare) was packed in a 0.66 cm×˜30 cm column. The column was equilibrated with a 140 mM Tris/Acetate buffer at the targeted pH and conductivity (Table 3). After equilibration, the column was loaded with each pre-conditioned feed at a resin loading level about 34 to 40 g/L followed by a 2 CV equilibration buffer wash. The displacing buffer, which consists of defined concentration of protamine sulfate in the equilibration buffer, was flowed through the column to initiate the displacement process. This step was continued for 30 CV at a flow rate corresponding to ˜22 min RT before column regeneration and cleaning. Sample fractions were collected at every 0.5 or 1 CV for protein concentration and quality analysis. The specific processing conditions are detailed in Table 3.

The levels of acidic species and other charge variants in the Adalimumab, mAb X and mAb Y samples were quantified using the respective qualified CEX-HPLC method. For Adalimumab, a 4 mm×250 mm analytical Dionex ProPac WCX-10 column (Dionex, CA) was used along with a Shimazhu HPLC system. The mobile phases were 10 mM Sodium Phosphate dibasic pH 7.5 buffer (Mobile phase A) and 10 mM Sodium Phosphate dibasic, 500 mM Sodium Chloride pH 5.5 buffer (Mobile phase B). A binary gradient (6% B: 0 min; 6-16% B: 0-20 min; 16-100%B: 20-22 min; 100% B: 22-26 min; 100-6% B: 26-28 min; 6% B: 28-35 min) was used with detection at 280 nm. Quantitation was based on the relative area percentage of detected peaks. The peaks that elute at residence time less than ˜7 min were together represented as the acidic peaks or AR region.

For mAb X, a 4 mm×250 mm analytical Dionex ProPac WCX-10 column (Dionex, CA) was used along with a Shimazhu HPLC system. The mobile phases were 20 mM MES, pH 6.5 buffer (Mobile phase A) and 20 mM MES, 500 mM NaCl, pH 6.5 buffer (Mobile phase B). A binary gradient (10% B: 0 min; 10-28% B: 1-46 min; 28-100% B: 46-47 min; 100% B: 47-52 min; 100-10% B: 52-53 min; 10% B: 53-58 min) was used with detection at 280 nm. Quantitation was based on the relative area percentage of detected peaks. All peaks eluting prior to the Main Isoform peak were summed as the acidic region, and all peaks eluting after the Main peak were summed as the basic region.

For mAb Y, a 4 mm×250 mm Dionex ProPac analytical WCX-10 column (Dionex, CA) was used on a Shimazhu HPLC system. The mobile phases were 20 mM MES, pH 6.2 (Mobile phase A) and 20 mM MES, 250 mM NaCl, pH 6.2 (Mobile phase B). A binary gradient (1% B: 0-1 min; 1-25% B: 1-46 min; 25-100% B: 46-47 min; 100% B: 47-52 min; 100-1% B: 52-53 min; 1% B: 53-60 min) was used with detection at 280 nm. Column temperature was set at 35° C. Quantitation was based on the relative area percentage of detected peaks. All peaks eluting prior to the Main Isoform peak (but after 2 min retention time) were summed as the acidic region, and all peaks eluting after the Main peak were summed as the basic region.

The levels of aggregates, monomer and fragments in eluate samples were measured using a SEC method for each molecule. For Adalimumab and mAb Y, a TSK-gel G3000SWxL, 5 μm, 125 Å, 7.8×300 mm column (Tosoh Bioscience) was used while a TSK-gel Super SW3000, 4 μm, 250 Å, 4.6×300 mm column (Tosoh Bioscience) was used for mAb X along with an Agilent or a Shimazhu HPLC system. For Adalimumab and mAb X, injections were made under isocratic elution conditions using a mobile phase consisting of 100 mM sodium sulfate and 100 mM sodium phosphate at pH 6.8, and detected with UV absorbance at 214 nm. For mAb Y, the mobile phase consists of 1×PBS at pH 7.4, and elution profile detected with UV absorbance at 280 nm. Quantification is based on the relative area of detected peaks.

An HCP ELISA assay was used to determine the HCP levels in various samples and feeds for all three mAbs.

TABLE 1 Processing conditions for Poros XS one-step displacement chromatography Displacer Equilibration/Wash/Displacing buffer Conc. Conductivity Loading Molecule Displacer (mM) Buffer System pH (mS/cm) Conditions Regeneration Adalimumab Expell SP1 0.5-3 Tris/Acetate 6.7-7.8 5.4-6.6 pH ~7.5, ~6 mS/cm 2M NaCl   2-5 MES/NaCl 6.1 2.1 pH 6.1, ~2 mS/cm 0.2M acetic acid & 1M KCl Protamine 0.25-2  Tris/Acetate 6.5-7.5 5.6-6.6 pH 7.5, 5.4-6.3 mS/cm 2M NaCl, 6M Guanidine HCl Sulfate mAb X Expell SP1 0.5-2 Tris/Acetate 6 6.2-6.5 pH 6, ~6 mS/cm 2M NaCl Protamine  0.25-0.5 Tris/Acetate 6 6.0-6.5 pH 6, 5.6-6.5 mS/cm 2M NaCl, 6M Guanidine HCl Sulfate mAb Y Expell SP1 0.5-1 Tris/Acetate 5 ~6 pH 5, 6.2 mS/cm 2M NaCl

TABLE 2 Processing conditions for Poros XS two-step or linear gradient displacement chromatography Equilibration/Wash/ Displacer Displacing buffer Displacement Concentration Buffer Conductivity Loading Molecule Displacer Method (mM) System pH (mS/cm) Conditions Regeneration Adalimumab Expell SP1 Two-step (1): 0.5 mM, Tris/Acetate 7 ~6 pH 7.5, 6.1 mS/cm 2M NaCl 25CV; (2): 2 mM, 20CV Protamine Two-step (1): 0.25 mM, Tris/Acetate 7.5 5.5 pH 7.5, 6.1 mS/cm 2M NaCl, 6M Sulfate 10 CV; Guanidine HCl (2): 2 mM, 10CV Expell SP1 Linear 0-1 mM over Tris/Acetate 7 ~6 pH 7.5, 6.0 mS/cm 2M NaCl Gradient 40 CV Protamine Linear 0-1 mM over Tris/Acetate 7.5 ~6 pH 7.5, 5.9 mS/cm 2M NaCl, 6M Sulfate Gradient 40 CV Guanidine HCl mAb X Expell SP1 Two-step (1): 0.5 mM, Tris/Acetate 6 6.1 pH 6, 6.3 mS/cm 2M NaCl 22CV; (2): 2 mM, 12CV Protamine Two-step (1): 0.35 mM, Tris/Acetate 6 ~6 pH 6, 6.3 mS/cm 2M NaCl Sulfate 10CV; (2): 0.5 mM, 10CV

TABLE 3 Processing conditions for Capto MMC one-step displacement chromatography Equilibration/Wash/ Displacer Displacing buffer Concentration Buffer Conductivity Loading Molecule Displacer (mM) System pH (mS/cm) Conditions Regeneration CIP Adalimumab Protamine 0.25-0.5 Tris/Acetate 7-7.5 ~6 pH 7.5, 5.3-6.1 mS/cm 2M NaCl, 0.5N NaOH + Sulfate 6M 0.5M KCl Guanidine HCl mAb X Protamine 0.25-0.5 Tris/Acetate 7-7.7 ~6 pH 7-7.7, 5.9-6.5 mS/cm 2M NaCl, Sulfate 6M Guanidine HCl mAb Y Protamine 0.25-0.5 Tris/Acetate 5-5.5 ~6.5 pH 5.5, 5.2-5.6 mS/cm 2M NaCl, Sulfate 6M Guanidine HCl

5.1. Displacement chromatography performances of Expell SP1™ for Adalimumab on Poros XS Resin

Expell SP1™ is a low molecular weight quaternary ammonium salt that exhibited pronounced displacement effect for Adalimumab on Poros XS resin under selected sets of operating conditions. The feed material used for this set of experiments contained about 20-25% total AR, of which 2-5% was AR1 and 18-20% AR2. The results for this system are shown in the following sections.

A representative, desired displacement chromatographic profile is shown in FIG. 1a (solid line). In this experiment, the column was equilibrated with a pH 7 Tris/acetate buffer (6.4 mS/cm), loaded with a pre-adjusted protein A eluate feed (pH 7.5, 6.3 mS/cm, ˜3.4 g/L) to ˜40 g/L resin loading level, followed by EQ buffer wash and then displacement process using 1 mM Expell SP1™ in the pH 7 EQ buffer. The extended, square shape UV280 “elution” profile indicated establishing a proper displacement train and thus a degree of separation of the feed components can be realized.

FIG. 2 illustrates the CEX-HPLC chromatograms for several samples taken along this well-established displacement UV trace. Clearly, the variant species were rearranged during the displacement process according to their respective binding affinity to the resin: AR1 was enriched in the foremost of the displacement train followed by AR2, Lys0, Lys1 and Lys2 in order.

FIG. 3 shows the distribution of each variant species in all the collected sample fractions. The acidic species were enriched in the earlier fractions compared to the Lys variants. By excluding those earlier fractions the product pool AR level will be reduced relative to that in the feed. This is reflected in FIG. 4 which plots the reduction of total AR (i.e. AR1+AR2) and AR1 level versus cumulative product yield. At a yield of ˜75%, the total AR % was reduced by 11.7% and AR1% by 4.2% under this set of condition.

Varying the processing conditions such as the buffer pH and displacer concentration can modulate the shape of the displacement chromatogram and hence the separation performance. In an extreme case, the chromatogram more or less resembles the typical elution “peak” profile without incurring the separation of variant species (FIGS. 1a and 1b ). Interestingly, this occurs at stronger binding conditions; for instance, the conditions corresponding to FIG. 1b is pH 6.1 and ˜2 mS/cm for equilibration, loading, wash, and displacement. Without being bond by theory, the lack of variant separation under such conditions may be due to the diminishing difference in binding affinity of each species and thus the selectivity by the displacer.

The effect of Expell SP1™ concentration on Adalimumab AR reduction was measured in pH 7.5 Tris/Acetate buffer, as shown in FIG. 5. The same equilibration/wash and feed loading conditions were used for all the runs here. Increasing Expell SP1™ concentration from 0.5 to 3 mM decreased AAR % from 8.9% to 3.5% at similar product yield ˜75%. Controlling the Expell SP1™ concentration within 2 mM will consistently achieve ≧6% AR % reduction.

The effect of displacing buffer pH on AR reduction for Adalimumab was measured at 1 mM Expell SP1™ concentration in the Tris/Acetate buffer, as shown in FIG. 6. In this set of experiments, the column was conditioned with an EQ buffer at the respective displacing buffer pH, and then loaded with protein feed at pH 7.5 and ˜6 mS/cm followed by a brief EQ buffer wash before starting the displacement step. The buffer pH significantly impacts AR clearance in pH range of 6-8. At similar yield (˜75%), the maximal reduction in AR level (˜12%) is seen at pH 7. Despite such pH-dependency, the majority of the conditions here (pH 6.5 to 7.8) gave at least 5% AR removal in final product pool.

In the aforementioned experiments, one displacing buffer was used to achieve the protein variant separation. It was observed that, relatively lower displacer concentration gives better separation but tends to elongate the process due to substantial increase in the required displacing buffer volume. For instance, when using 0.5 mM Expell SP1™ in a pH 7 displacing buffer (Table 1), the displacement phase requires 44 column volumes (CV) of this buffer for completion. To accelerate the operation without affecting the acidic species separation, a two-step displacement process was explored at this pH condition. In the example provided here, the displacement process was started with 0.5 mM Expell SP1™ at pH 7 and continued for 25 CV, followed by 20 CV of 2 mM Expell SP1™ solution at the same pH. Under such conditions, the protein displacement profile was completed in a total of 33 CV which is 25% less than that required for one-step displacement process, thus significantly shortening the process.

FIG. 7 shows the reduction of AR % versus product yield for the aforementioned two-step displacement run. The net total AR level in product pool was reduced by 6.6% at ˜75% yield. In contrast to the conventional use of a single displacing solution consisting of a single displacer at a defined concentration, herein the AR clearance was achieved by excluding the AR-enriched early fractions as induced by 0.5 mM Expell SP1™ displacement, while the higher Expell SP1™ concentration was used to accelerate the displacement of the remainder proteins off the solid phase. In light of this unexpected similar product quality and yield results, step-gradient displacement schemes are considered to be advantageous over conventional strategies.

Besides the two-step displacement scheme, a linear gradient displacement method was also tested for the Adalimumab charge variant separation. As detailed in Table 2, after the feed loading at pH 7.5 (˜6 mS/cm), the column was briefly washed with the equilibration buffer (pH 7, ˜6 mS/cm) and then started with a 40 CV linear gradient from the EQ buffer to a 1 mM Expell SP1™ displacing buffer (which was made from the EQ buffer). Under such condition, the displacement profile matured within this 40 CV gradient. The product eluate was pooled by excluding the first a few fractions. In this case, the net AR % decreased by 6.8% at a product recovery of 72%.

Apart from acidic species, other product- or process-related impurities can be effectively separated by Poros XS displacement chromatography using Expell SP1™ as the displacer. FIG. 8 shows the separation of aggregates, monomer and fragments in Adalimumab sample fractions obtained from a one-step displacement experiment using 1 mM Expell SP1™ pH 7 buffer. It should be noted that the last two fractions from this run were not collected, therefore the increased aggregate levels at the end of the displacement train was not fully exemplified here. Interestingly, the early fractions which contained elevated acidic species also showed enriched aggregates, indicating that this population of aggregates may consist of more acidic species, or the acidic species has higher propensity to form aggregates. As summarized in Table 4, the aggregate level in the product pool (at ˜75% yield) was reduced from the feed level 1.16% to 0.11% and the fragment level down to 0.04% along with significant reduction in the AR concentration. In addition to the standard method, the linear gradient displacement run also showed aggregate reduction from the feed level of 0.9% to about 0.2% in final product.

FIG. 9 shows the distribution of HCP in the Adalimumab displacement train coming off the Poros XS column. Relatively higher level of HCP was observed at both ends of the train, due to their diverse charge characteristics and associated binding strength. The final product pool HCP level was reduced to 5 ng/mg from the starting feed, representing approximately 50-fold reduction.

TABLE 4 Step yield & product quality in Adalimumab before and after Poros XS displacement chromatography using Expell SP1 ™ (pH 7, 1 mM Expell SP1 ™) HCP Yield % AR1% AR2% Lys Sum % HMW % Monomer % LMW % (ng/mg) Feed — 4.3 17.8 77.9 1.16 98.57 0.27 267 Product 74 0.1 10.3 89.6 0.11 99.85 0.04 5 pool

5.2. Displacement Chromatography Performance of Protamine Sulfate for Adalimumab on Poros XS Resin

Protamine sulfate, a cationic peptide with molecule weight ˜5.1 kD, was also evaluated as a cation exchange displacer for Adalimumab on Poros XS resin under various operating conditions. The feed material used for this set of experiments contained about 17-24% total AR, of which 3-6% was AR1 and 14-19% AR2. The results for this system are illustrated in the following sections.

FIG. 10 shows the distribution of charge variant species in sample fractions collected from a well established displacement process induced by protamine sulfate. In this experiment, the column was equilibrated with a pH 7.5 Tris/acetate buffer (5.6 mS/cm), loaded with a pre-adjusted protein A eluate feed (pH 7.5, 5.4 mS/cm, 5.2 g/L) to 39 g/L resin loading level, followed by a brief EQ buffer wash and then displacement process using 0.5 mM protamine sulfate dissolved in the pH 7.5 EQ buffer. Similar to the Expell SP1™ displacement profile (FIG. 3), the charge variants were enriched at different locations of the displacement train and were peaked in the order of AR1, AR2, Lys0, Lys1 and Lys2. The cumulative AR % reduction as a function of product yield is illustrated in FIG. 11. A 6-8% decrease in the total AR level can be obtained at a yield of 75-85% under this set of condition. The actual levels of AR1, AR2 and total Lys (i.e. Lys0+Lys1+Lys2) for the feed and the final product pool are shown in Table 5.

The effect of protamine sulfate concentration on Adalimumab AR reduction was measured in pH 7.5 Tris/Acetate buffer, as shown in FIG. 12. The same equilibration/wash and feed loading conditions as described above were used for all the runs here. At similar yield (˜75%), the total AR % was reduced by approximately 7-8% when using 0.25 to 2 mM protamine sulfate. This broad concentration range reflects the robustness of charge variant separation by protamine sulfate displacement process.

The effect of displacing buffer pH on AR clearance for Adalimumab was measured at 0.5 mM protamine sulfate concentration in Tris/Acetate buffer. In this set of experiments, the column was conditioned with an EQ buffer at the respective displacing buffer pH, loaded with protein feed at pH 7.5 and ˜6 mS/cm followed by a brief EQ buffer wash before starting the displacement phase. As shown in FIG. 13, the extent of AR reduction increases significantly as pH varies from 6.5 to 7.5. Over 6% decrease in AR level can be achieved at pH 7.5 with a product yield ˜75%.

The two-step displacement scheme was also tested with protamine sulfate. In one experiment, the displacement process consists of 10 CV of 0.25 mM protamine and 10 CV of 2 mM protamine at pH 7.5 (Table 2). The protein displacement profile was completed in a total of 13 CV, which is about 11 CV or almost 2 fold shorter than that in the one-step displacement process with 0.25 mM protamine sulfate. The reduction of AR % versus product yield is shown in FIG. 14. The total AR level in product pool were reduced by ˜8% at ˜75% yield, which is comparable to that achieved by the one-step displacement process using 0.25 mM protamine sulfate.

The linear gradient displacement scheme was also evaluated with protamine sulfate on Poros XS resin for Adalimumab charge variant separation. As summarized in Table 2, after the feed loading at pH 7.5 (5.9 mS/cm), the column was briefly washed with the equilibration buffer (pH 7.5, ˜6 mS/cm) and then started with a 40 CV linear gradient from the EQ buffer to a 1 mM protamine sulfate displacing buffer (which was made from the EQ buffer). FIG. 15 shows the cumulative AAR % versus yield from this run. At a product yield of 75.6%, the total AR % was reduced from the feed level of 21.3% to 12.1%.

Protamine sulfate displacement chromatography also demonstrated significant clearance of aggregates, fragments and HCP. FIG. 16 exemplifies the size variant profiles of Adalimumab from the same experiment described above (i.e., 0.5 mM protamine sulfate, pH 7.5, one-step displacement run). As expected, the fragments were mostly enriched at the front while the aggregates primarily resided at the back of the train. Similar to that shown in FIG. 8, a subpopulation of the aggregates was also observed in the displacement front; in addition, a portion of fragments was noticed at the tail. Table 5 compares the levels of aggregates, fragments and HCP in final product pool (at ˜75% yield) relative to the feed.

TABLE 5 Step yield & product quality in Adalimumab before and after Poros XS displacement chromatography using protamine sulfate Yield % AR1% AR2% Lys Sum % HMW % Monomer % LMW % HCP (ng/mg) Feed — 4.1 16.9 79.0 0.8 98.0 1.2 153 Product pool 73 1.3 13.1 84.7 0.3 99.6 0.1 14

5.3. Displacement Chromatography Performance of Expell SP1™ for mAb X on Poros XS Resin

The displacement separation performance of Expell SP1™ was assessed for mAb X on the Poros XS resin. A purified mAb X drug substance was used in this study, which contained about 16-17% acidic species and 12-14% basic species.

A representative set of mAb X charge variant separation profiles are shown in FIGS. 17 and 18. In this experiment, the Poros XS column was loaded with 40 g/L of mAb X at pH 6, 6 mS/cm Tris/Acetate binding condition, and was displaced using 1 mM Expell SP1™ in a pH 6, ˜6 mS/cm buffer. The specific conditions are detailed in Table 1. Pronounced enrichment and separation of acidic, main and basic species were achieved, with AR % reduced by 9.4% at 76% yield.

The effect of Expell SP1™ concentration on AR reduction for mAb X was measured in the pH 6 Tris/Acetate buffer. As shown in FIG. 19, increasing the Expell SP1™ concentration from 0.5 to 2 mM decreased the AAR % for mAb X from 9.8% at 81% yield to 7.9% at 69% yield.

The two-step displacement scheme was evaluated for mAb X. As shown in Table 2, the displacement process comprised of 22 CV of 0.5 mM Expell SP1™ and 12 CV of 2 mM Expell SP1™ at pH 6. The protein displacement profile was completed within 30 CV of total displacing buffer volume, which was 30% less than that required for one-step displacement separation. The reduction of AR % versus product yield is shown in FIG. 20. The total AR % in product pool was reduced by ˜9% at ˜75% yield, again comparable to that obtained with one-step displacement process using 0.5 mM Expell SP1™ buffer.

5.4. Displacement Chromatography Performance of Protamine Sulfate for mAb X on Poros XS Resin

Protamine sulfate was also evaluated for separating acidic species for mAb X on Poros XS resin. The feed material for this set of experiments contained about 12-16% acidic and 12-13% basic species. The results for this system are shown in the following sections.

A representative set of variant separation profiles are shown in FIGS. 21 and 22. In this experiment, the Poros XS column was loaded with ˜36 g/L of mAb X at pH 6, 6.5 mS/cm binding condition, and was displaced using 0.25 mM protamine sulfate in a pH 6, 6.5 mS/cm Tris/Acetate buffer. The specific conditions are detailed in Table 1. Pronounced enrichment and separation of acidic, main and basic species were achieved, with AR level reduced by 6% at 75% yield.

The effect of protamine sulfate concentration on mAb X AR reduction was measured in a pH 6 Tris/Acetate buffer, as shown in FIG. 23. In this case, the protamine sulfate concentration strongly affects the AR clearance in a relatively small protamine concentration range (i.e. from 0.35 to 0.5 mM). Nevertheless, over 8% of AR reduction can be achieved at pH 6 for mAb X at acceptable yield (≧70%).

The two-step displacement scheme was evaluated for mAb X with protamine sulfate. In this experiment, the displacement process comprised of 10 CV of 0.35 mM Expell and 10 CV of 0.5 mM Expell at pH 6 (see Table 2). The protein displacement profile was completed in ˜15 CV of total displacing buffer volume, representing ˜26% reduction of buffer volume relative to the one-step displacement operation. The reduction of AR % versus product yield is shown in FIG. 24. The product pool AR level was reduced by ˜6% at ˜75% yield.

The mAb X BDS has about 0.74% of aggregates, which can be further reduced during the protamine sulfate displacement process. FIG. 25 shows the size variant profiles of mAb X as displaced by a 0.25 mM protamine sulfate, pH 6 buffer (i.e., the one-step displacement run shown in FIGS. 21 and 22). The aggregates were all enriched at the end of the displacement train, which differs from the observations with Adalimumab. Using the same product pooling strategy based on AR reduction, the monomer level was enhanced to 99.9% (Table 6).

TABLE 6 Step yield & product quality in mAb X before and after Poros XS displacement chromatography using protamine sulfate Yield % Acidic % Main % HMW % Monomer % Feed — 12.3 75.7 0.7 99.3 Product pool 79 4.7 80.8 0.1 99.9

5.5. Displacement Chromatography Performance of Expell SP1™ for mAb Y on Poros XS Resin

The displacement separation performance of Expell SP1™ was further assessed for mAb Y on Poros XS resin. The mAb Y has a pI of 7-7.5, much lower than Adalimumab and mAb X. An mAb Y protein A eluate was used in this study, which contained about 22% acidic species and 15% basic species.

An appropriate set of displacement conditions for mAb Y is shown in Table 1. The equilibration, wash and displacement buffers are all at pH 5 with conductivity around 6 mS/cm. The 0.5 mM Expell SP1™ buffer generated the desired displacement profile. The sample fractions from this run were analyzed by cation exchange HPLC. FIGS. 26 and 27 indicate the distribution of charge variant species and the cumulative AAR % versus product yield, respectively. A 6.6% decrease in AR % was observed at 74% yield under such condition.

5.6. Displacement Chromatography Performance of Protamine Sulfate for Adalimumab on Capto MMC (Multimodal) Resin

Capto MMC™ is a mixed mode resin based on weak cation-exchange and hydrophobic interaction mechanism. Its capability for acidic species and aggregates removal by displacement chromatography was assessed here. The Adalimumab feed material for this set of experiments contained about 20-21% total AR. The results for protamine sulfate system are shown in the following sections.

A representative set of variant separation profiles are shown in FIGS. 28 and 29. In this experiment, the Capto MMC column was equilibrated with a 140 mM Tris/acetate, pH 7 buffer (˜5.7 mS/cm), loaded with ˜34 g/L of Adalimumab at pH 7.5 and 5.3 mS/cm binding condition, briefly washed with EQ buffer and then displaced with 0.35 mM protamine sulfate in the pH 7 EQ buffer. A typical displacement chromatogram was generated under such experimental condition. As shown in FIG. 10, Capto MMC also showed enrichment of each variant in the train, yielding total AR reduction of ˜4% at ˜75% yield. The shape of the AAR % versus yield curve (FIG. 29) differs from that given by the Poros XS resin, possibly due to stronger binding of each protein species (related to secondary mode of interaction) by this mixed mode ligand.

The buffer pH and protamine sulfate concentrations were varied to assess the overall AR clearance by Capto MMC displacement chromatography. Table 7 summarized the results for three runs. Overall, 3-5% of AR reduction can be achieved for Adalimumab when using protamine sulfate as a displacer for Capto MMC resin.

TABLE 7 AR removal for Adalimumab by Capto MMC displacement chromatography using protamine sulfate EQ/Displacing Protamine Run buffer Load Conc. Yield ΔAR No. pH pH (mM) (%) % 1 7 7 0.5 75 3.1 2 7 7.5 0.35 75 4.0 3 7.25 7.5 0.25 78 5.2

The clearance of aggregates by Capto MMC displacement chromatography is illustrated in Table 8. The same operating conditions as described for obtaining the results in Table 7 were used here. The product pool monomer level was enhanced from 98.8% in the feed to 99.4% with aggregates reduced from 1.0% to 0.5%.

TABLE 8 Step yield & product quality in Adalimumab before and after Capto MMC displacement chromatography using protamine sulfate Yield % AR1% AR2% Lys Sum % HMW % Monomer % LMW % Feed — 4.4 16.5 79.1 1.0 98.8 0.2 Product 75 2.5 14.4 83.1 0.5 99.4 0.1 pool

5.7. Displacement Chromatography Separation of Protamine Sulfate for mAb X on Capto MMC Resin

Protamine sulfate was evaluated for removing mAb X acidic species on Capto MMC resin. The same feed material as shown in Section 5.4 was used for this set of experiments. As detailed in Table 3, the pH and protamine concentrations were varied in order to generate desired displacement profile. One representative set of working condition is to load Capto MMC column with 40 g/L of mAb X at pH 7.5 and ˜6 mS/cm, and to use 0.25 mM protamine sulfate in the pH 7.5, ˜6 mS/cm EQ buffer for displacement (Table 3). The separation of charge variants and AR reduction as a function of product recovery are shown in FIGS. 30 and 31, respectively. In this case, 3-5% of AR reduction was resulted at product yield of 70-90%.

The effect of protamine sulfate concentration on mAb X AR reduction by Capto MMC resin was measured in a pH 7, 6 mS/cm Tris/Acetate buffer, as shown in Table 9. Varying the protamine concentration from 0.25 mM to 0.5 mM had very little effect on AAR % and product yield, which is quite different from the observations with the Poros XS resin (FIG. 23). The mixed mode MMC resin gave over 3% AR clearance under such selected conditions.

TABLE 9 Reduction of AR level by Capto MMC displacement chromatography for mAb X at different protamine sulfate concentrations Expell concentration Yield ΔAR (mM) (%) (%) 0.25 75 3.4 0.5 77 3.3

The effect of displacing buffer pH on AR clearance for mAb X was measured at 0.25 mM protamine sulfate concentration in Tris/Acetate buffer. In this set of experiments, the column was conditioned with an EQ buffer at the respective displacing buffer pH, loaded with protein feed at the same pH and ˜6 mS/cm followed by a brief EQ buffer wash before starting the displacement phase. As shown in FIG. 32, AAR % increases from 3.3 to 6.5% as pH varies from 7 to 7.7.

The Capto MMC resin also removes aggregates during protamine sulfate displacement chromatography. Table 10 shows the level of charge and size variants of mAb X in product eluate when using 0.5 mM protamine sulfate, pH 7.5 (˜6 mS/cm) displacing buffer for separation. The product pool monomer level was enhanced from 98.7% in the feed to 99.2% with aggregate and fragment levels reduced by 50% and 28%, respectively.

TABLE 10 Step yield & product quality for mAb X before and after Capto MMC displacement chromatography using protamine sulfate Yield Acidic % % Main % HMW % Monomer % LMW % Feed — 16.8 74.0 0.6 98.7 0.7 Product 77 12.4 71.8 0.3 99.2 0.5 pool

5.8. Displacement Chromatography Separation of Protamine Sulfate for mAb Y on Capto MMC Resin

Protamine sulfate was also evaluated for removing mAb Y acidic species on Capto MMC resin. The same feed material as shown in Section 5.5 was used for the experiments here. Two sets of conditions were evaluated here. In one experiment, the equilibration, wash and displacement buffers were adjusted to pH 5.5 and ˜6.5 mS/cm, and the displacement buffer contained 0.25 mM protamine sulfate. In the other experiment, all those buffers were adjusted to pH 5, ˜6.5 mS/cm and the protamine sulfate concentration was 0.5 mM. In both runs the feed was adjusted to pH 5.5, 5.2-5.5 mS/cm and loaded to the Capto MMC column at ˜40 g/L loading level. As shown in Table 11, both sets of conditions resulted in AR % decrease by 5-7% in product pool. In addition, significant aggregates and fragments reduction was achieved with the same product pooling strategy.

TABLE 11 Step yield & product quality for mAb Y before and after Capto MMC displacement chromatography using protamine sulfate Conditions Sample Yield % Acidic % Main % HMW % Monomer % LMW % pH 5.5, 0.25 mM Feed — 16.4 75.8 8.5 91.0 0.5 Protamine Product 76 9.8 79.4 2.0 97.6 0.4 pool pH 5, 0.5 mM Feed — 20.9 72.8 6.3 93.2 0.5 Protamine Product 75 15.9 81.1 1.6 98.2 0.2 pool

Sections 5.1. to 5.8, above, demonstrate the use of cation exchange and mixed mode displacement chromatography for effectively reducing acidic species along with various other impurities from different mAb feed streams. Under appropriate (or relatively weak) binding conditions, cationic molecules with high affinity for a CEX or multimodal ligand (such as Expell SP1™ and protamine sulfate) can induce the formation of charge variant displacement train, wherein the acidic population is enriched in the front followed by the main isoform, and, thereafter, the basic population. Thus, in certain embodiments, exclusion of those earlier fractions from the remainder eluate results in an AR-reduced product. Alternatively, exclusion of the fractions following the main isoform results in a Lys variant- or basic species-reduced product.

Also demonstrated in the preceding experiments is the fact that the operating pH and displacer concentration can strongly affect the displacement profile and as a result the charge variant, product aggregate, product fragment, and HCP clearance profile. The selection of a particular operating regime with regard to charge variant reduction depends, in general, on the specific protein-resin-displacer system. For example, for Adalimumab, significant AR reduction can be achieved using a displacing buffer with pH in the range of 6-8 with displacer concentration as low as 0.25-0.5 mM. The total AR level (%) in Adalimumab product pool can be reduced by over 10% with an acceptable processing yield (≧75%) from a CEX displacement chromatography process, or 4-7% from a mixed mode displacement chromatography process. Along with acidic species, other product variants or process impurities such as basic species, aggregates, fragments and HCP can be selectively collected or reduced to meet the quality requirements. In addition to the surprisingly effective preparative scale standard one-step displacement operation, unconventional displacement separation schemes are shown above to have unexpected properties, including two-step displacement chromatography and linear gradient displacement chromatography, which can significantly reduce buffer volumes and shorten the processing time without compromising the charge variant, product aggregate, product fragment, and HCP clearance at a given yield target.

5.9 Utility of AR Reduction

The current invention provides a method for reducing acidic species for a given protein of interest. In this example adalimumab was prepared using a combination of AEX and CEX technologies to produce a Low-AR and High-AR sample with a final AR of 2.5% and 6.9%, respectively. Both samples were incubated in a controlled environment at 25° C. and 65% relative humidity for 10 weeks, and the AR measured every two weeks. FIG. 23 shows the growth of AR for each sample over the 10 week incubation. It is evident from FIG. 23 the growth rate of AR is linear and similar between both the Low-AR and High-AR samples. Based on these results the reduced AR material can be stored 3 fold longer before reaching the same AR level as the High-AR sample. This is a significant utility as this can be very beneficial in storage handling and use of the antibody or other proteins for therapeutic use.

Patents, patent applications, publications, product descriptions, GenBank Accession Numbers, and protocols that may be cited throughout this application, the disclosures of which are incorporated herein by reference in their entireties for all purposes. For example, but not by way of limitation, patent applications designated by the following attorney docket numbers are incorporated herein by reference in their entireties for all purposes: 082254.0235; 082254.0236; 082254.0238; 082254.0242; and 082254.0243. 

We claim:
 1. A method for reducing process-related impurities and/or product-related substances in a preparative scale sample of a protein of interest comprising at least one process-related impurities and/or product-related substance, the method comprising: (a) contacting the sample to a chromatography media under conditions wherein the protein of interest binds to the chromatography media; (b) displacing the protein of interest bound to the chromatography media with a displacer buffer comprising at least one displacer molecule; and (c) collecting a chromatography sample, wherein the chromatography sample comprises a reduced amount of process-related impurities and/or product-related substances.
 2. The method of claim 1, wherein the chromatography media is an ion exchange adsorbent material.
 3. The method of claim 1, wherein the chromatography media is a multimodal adsorbent material comprising cation exchange and hydrophobic interaction functional groups.
 4. The method of claim 1, wherein the pH of the displacing wash buffer is lower than the isoelectric point of the protein of interest.
 5. The method of claim 1, wherein the displacer in the wash buffer carries positive charge and wherein the concentration of the displacer in the wash buffer is greater than 0.1 mM.
 6. The method of claim 2, wherein the cation exchange (CEX) adsorbent material is selected from the group consisting of a CEX resin and a CEX membrane adsorber.
 7. The method of claim 4, wherein the pH of the displacing wash buffer is in the range of about 6.0 to about 8.0.
 8. The method of claim 1, wherein the conductivity of the wash buffer is in the range of about 2 to about 20 mS/cm.
 9. The method of claim 1, wherein the column length is in the range of about 10 cm to about 30 cm and the flow residence time is in the range of about 5 min to about 25 min.
 10. The method of claim 5, wherein the cationic displacer in the wash buffer is a quaternary ammonium salt and the concentration of the displacer in the wash buffer is in the range of 0.1 to 10 mM.
 11. The method of claim 5, wherein the cationic displacer in the wash buffer is protamine sulfate and the concentration of the protamine sulfate in the wash buffer is in the range of 0.1 to 5 mM.
 12. The method of claim 1, wherein two or more displacing buffers consisting of different displacer concentrations are used.
 13. The method of claim 12, wherein the first displacing buffer containing lower displacer concentration than the second or later displacing buffer.
 14. The method of claim 1, wherein the displacement operation is run in two-step displacement chromatography mode.
 15. The method of claim 1, wherein the displacement operation is run in multiple-step or linear displacement chromatography mode.
 16. The method of claim 14, wherein the first displacing buffer containing 0.5 mM Expell SP1™.
 17. The method of claim 14, wherein the first displacing buffer containing 0.25 mM protamine sulfate.
 18. A composition comprising a protein of interest and a reduced level of protein aggregates.
 19. A composition comprising a protein of interest and a reduced level of protein fragments.
 20. A composition comprising a chromatographic sample of claim 1, wherein the composition comprises a reduced level of host cell proteins.
 21. A composition comprising a chromatographic sample of claim 1, wherein the composition comprises levels of basic variants that differ from the starting load material.
 22. The method of claim 1, wherein the protein of interest is an anti-TNFα antibody. 